On Monday morning, Apple (NASDAQ:AAPL) revealed that it had set a new record for iPhone launch weekend sales, selling more than 13 million iPhone 6s and 6s Plus models between Friday and Sunday. As my Foolish colleague Daniel Sparks pointed out, this announcement wasn't a big surprise, as Apple had already predicted that it would set a new iPhone sales record.

G

Apple sold more than 13 million iPhone 6s and iPhone 6s Plus units last weekend. Source: Apple.

While this number seems very impressive, investors didn't seem to care. Apple stock fell along with the broader market on Monday. That's because while the first weekend sales number is grabbing the headlines, a few other statistics are much more important for assessing Apple's performance.

What the naysayers are saying
Apple's strong opening-weekend iPhone sales number didn't sway Apple bears because it doesn't reveal much about underlying iPhone demand trends.

First, new iPhone introductions always lead to a short-term surge in demand. Second, upon launching new models, Apple needs to sell millions of iPhones to its channel partners (e.g., wireless carriers and electronics retailers) to build up their inventories. Third, the iPhone wasn't available in China -- Apple's second-largest market -- on launch weekend in 2014, but China was part of the first wave of launches this year.

As a result, Apple's launch-weekend sales figure says more about supply than demand. Last year, Apple sold more than 10 million iPhones on launch weekend -- but given that it sold nearly 75 million iPhones in the following quarter, Apple easily could have moved 20 million units during the first weekend if it had adequate supply.

Thus, a 30% increase in first-weekend sales doesn't mean Apple is seeing 30% higher demand. The availability of the iPhone in China this year probably drove most of the increase. After accounting for differences in the sales backlogs, it seems likely that end-demand for the iPhone 6s is lower than iPhone 6 demand was at this time last year.

Indeed, Forbes contributor Ewan Spence asserts that iPhone 6s activations were down 40% from the iPhone 6 during launch weekend, using data from Fiksu. (iPhone 6s Plus activations were in line with 2014 iPhone 6 Plus activations, according to Spence.) This probably misreads the data, though, because Fiksu measures usage of each model as a percentage of the total iPhone base.

The iPhone user base has grown significantly in the past year due to the tremendous success of the iPhone 6 and iPhone 6 Plus. Additionally, Fiksu's data mainly captures activity in the U.S. and Europe, so the addition of China to this year's launch is probably not captured in the data. Taking these factors into account, end-user demand for the new iPhones may be down slightly year over year, but not by much.

The numbers that really matter
If Apple's strong opening-weekend sales figure couldn't dispel the cloud that has been hanging over Apple stock lately, what could turn the tide?

First, Apple needs to provide more evidence that it can grow iPhone sales in the new 2016 fiscal year despite facing tough comparisons. It will get its first opportunity next month, when it reports its September quarter earnings.

Most analysts are predicting a significant slowdown from the 35% iPhone unit growth Apple posted in the June quarter due to slowing demand for the iPhone 6 generation and the late launch of the iPhone 6s and 6s Plus. If Apple sold at least 50 million iPhones last quarter (equal to 27% year-over-year growth), it would show that demand for the iPhone 6 and iPhone 6 Plus held up well through the whole cycle, and that slowing economic growth in China isn't hurting Apple.

G

How well are iPhone 6 sales holding up? Source: Apple.

That would also bode well for iPhone sales in the coming year. If the iPhone 6 and iPhone 6 Plus found plenty of takers at full price last quarter, they should continue to sell well in FY16 after being marked down by $100. This means Apple could grow its iPhone sales by boosting sales of older, discounted models, even if demand for top-of-the-line models is flat compared to last year.

Second, Apple needs to generate significant growth in non-iPhone revenue. Investors haven't rewarded Apple for its 25%+ revenue growth in FY15 in part because more than 100% of that growth came from the iPhone (i.e., non-iPhone revenue declined year over year), increasing Apple's dependence on a single product.

However, Apple could reverse that in FY16, with non-iPhone revenue outgrowing iPhone revenue by a wide margin. Key non-iPhone revenue growth drivers include 1) the first holiday quarter for the Apple Watch; 2) a potential Apple Watch 2 launch in 2016; 3) Apple has recently updated the iPod touch and Apple TV for the first time since 2012; 4) the new iPad Pro could reinvigorate iPad revenue growth; and 5) the Mac continues to gain share against PCs.

We will get some hints on Apple Watch, iPod, and Mac demand in the upcoming earnings report. However, Apple's holiday quarter results will be the big test, because the new Apple TV and the iPad Pro will go on sale during the quarter, and Apple Watch could potentially be a big gifting item.

By and large, investors are not a patient bunch. However, the simple fact is that the most important information for assessing Apple's prospects for 2016 isn't available yet -- and it won't be until Apple releases its earnings report and holiday-quarter forecast next month.

Adam Levine-Weinberg is long January 2016 $80 calls on Apple, short January 2016 $120 calls on Apple, and short January 2016 $140 calls on Apple. The Motley Fool owns and recommends Apple. Try any of our Foolish newsletter services free for 30 days. We Fools may not 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.