You've probably heard lots of numbers thrown around lately pertaining to Obamacare. Some of those numbers are relevant to better understanding how things are going with the landmark health-reform legislation. Others, though, aren't all that important. Here are three Obamacare numbers that really don't count for much -- and one that absolutely does.

Source: WhiteHouse.gov.

1. Number of website bugs fixed
Jeffrey Zients, the official brought in to oversee the salvage effort for the HealthCare.gov website, stated this past week that programmers fixed more than 400 bugs. That sounds like an impressive number, especially considering that they accomplished this in less than two months. But that number actually means nothing.

A little more than a month ago, Health and Human Services Secretary Kathleen Sebelius said that "a couple of hundred" fixes were required to the website. Whether the figure was 200 or 400 or 4 million is irrelevant. What's really critical is how many bugs remain unfixed. And that's a number we simply don't know at this point.

2. Number of visitors
Federal officials said that more than 1 million Americans visited the site on the first business day following the Nov. 30 deadline for resolving many of the problems that plagued the Obamacare website during its first two months of operation. The next day brought more than 950,000 visitors. Those numbers, however, are inconsequential in the big scheme of things.

How can the number of visitors to the website not be critical? Granted, the number can make a difference -- especially if the volume results in significant slowdowns. But the primary thing to understand here is that the number of visitors doesn't matter. Actual enrollment figures matter.  

We saw in the early period of operation with HealthCare.gov that lots of Americans visited the site -- 4.7 million on the first day alone. However, relatively few enrolled in health plans. Think back to the heady dot-com days around 15 years ago. Many companies claimed that it was the number of eyeballs that counted. Most of them ultimately discovered, however, that eyeballs don't automatically result in success.  

3. Number of "sign-ups"
Official enrollment numbers haven't been released yet for November, but initial estimates are that around 100,000 signed up on HealthCare.gov. Figures for December will surely be higher, since the website is operating more reliably than in the past. In reality, though, those numbers don't count for much.

You're probably thinking: "Wait a second. Didn't you just say it's the actual enrollment numbers that matter?" Yes, you did read that -- and it's true. The problem is that the number of "sign-ups" provided thus far aren't the actual enrollment numbers.

The figures released so far from Health and Human Services reflect the number of Americans who have selected a health plan. However, people aren't actually enrolled with an insurance company (in most cases, anyway) until they pay the first premium. And we don't yet know how many of the Obamacare "sign-ups" have paid.

What we do have is some related anecdotal data. Physicians Health Plan of Northern Indiana, for example, said that only around 20% of its Obamacare applicants have paid. That shouldn't be too surprising. According to Web researcher Baymard Institute, two-thirds of website shoppers who select items for purchase don't end up buying those items.

The magic number
There is one number that's of utmost importance for Obamacare. This statistic is so important that the success or failure of the health reform legislation depends on it. What is this magic number? The number of young, healthy Americans who really enroll in Obamacare health plans.

Fear about what this number might be had some big names shying away from jumping fully on board with the health exchanges. UnitedHealth Group (NYSE: UNH) CEO Stephen Hemsley expressed concern months ago that too few of the initial wave of enrollees would be healthy. Not surprisingly, UnitedHealth opted to limit its participation in state exchanges.

Aetna (NYSE: AET) CEO Mark Bertolini raised this issue after the initial HealthCare.gov launch debacle. Bertolini worried aloud that younger Americans would be less likely to give the website a second chance. He noted that if enough people, particularly healthy individuals, don't sign up, major problems will ensue.

The core issue is that insurance companies rely on healthier members to effectively subsidize the costs of less healthy members. If there aren't enough healthy members, insurers lose money. The insurers then raise premiums, which can cause even fewer healthy individuals to buy the insurance. This ultimately can result in what is known as a "death spiral," in which the insurance plan becomes unviable.

Not every health insurance company felt such anxiety. WellPoint (NYSE: WLP), the nation's second-largest health insurer, jumped wholeheartedly on the Obamacare bandwagon. The company chose to participate in the exchanges of every state where it operates.

Will millions of young Americans enroll in Obamacare plans and prove WellPoint right? Three numbers are key to the answer for this question: 3, 31, and 14. Open enrollment ends on March 31. Only then will we know the number that really counts for Obamacare.

One Obamacare number that's great news for you
Zero. That's an Obamacare-related number you can smile about. It's the cost of our report called "Everything You Need to Know About Obamacare." This special free report explains the critical facts about Obamacare and how they impact you. Don't hesitate, though. It's not often that we release a free guide containing this much information and money-making advice. Simply click here to access your free copy now.

Fool contributor Keith Speights has no position in any stocks mentioned. The Motley Fool recommends UnitedHealth Group and WellPoint and owns shares of WellPoint. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.