Apple (AAPL -2.71%) threw investors a curve when it released a preview of its first-quarter financial results earlier this month. In a letter to shareholders penned by CEO Tim Cook, the company revised its guidance for the important holiday quarter, sending shares down about 10% in the wake of the announcement.

The bad news? Apple said revenue would come in at $84 billion, about $5 billion less than the low point of its previous guidance. Cook blamed the shortfall on a number of factors, including difficult year-over-year comps and economic weakness in emerging markets -- particularly in greater China.

Apple is sure to provide more details when it releases its full first-quarter earnings report, which is scheduled on Jan. 29, after the market close. Let's recap some of the other areas worth watching in light of its disappointing revenue miss.

A crowd of people in front of the Apple store in Singapore.

Image source: Apple.

Share repurchases

Apple has been repurchasing shares hand over fist, and likely went on a buying binge in the wake of its falling stock price. In the fourth quarter, it bought back more than 92 million shares at a cost of $19.4 billion, paying about $210 per share. Shares lost as much as a third of their value in the closing three months of 2018, giving it the opportunity to buy its shares at a significant discount.

The company disclosed in a recent regulatory filing that as of Sept. 29, 2018, Apple had used $29 billion of the $100 billion share repurchase authorization approved by the board in May. That left a whopping $71 billion available to buy back shares. 

Expect to hear details on buybacks when Apple reports earnings.

Earnings per share

The aforementioned proclivity for buying back its shares will likely help Apple increase its earnings per share. Over the past five years, it's reduced its share count by more than 20%. This benefits shareholders because the company's income is divided among fewer shares, increasing its EPS.

Cook alluded to this fact in the letter. Even though the company is reporting billions less in revenue, he said "We also expect to report a new all-time record for Apple's earnings per share." For reference, it reported record earnings per share of $3.89 during its fiscal 2018 first quarter. In line with Cook's pronouncement, the number this time around should be higher than that record. 

Record revenue in some segments

Even in light of the challenges Apple faced, Cook did focus on a few highlights. Apple achieved "all-time record revenue from Services, Wearables and Mac," according to Cook. We don't have to look back too far, as each of those segments had record-setting performances in Q4.

Apple sold 5.3 million Macs, generating revenue of $7.4 billion. Services revenue also saw its best quarter ever, at $9.98 billion. Based on those numbers and the figures from the company's 2018 fiscal first quarter, that should result in year-over-year growth of at least 7% and 18%, respectively for the Mac and services segments.

An Apple Watch taking a heart reading.

Image source: Apple.

Apple historically hasn't broken out revenue from wearables, which are part of its other products segment and includes the Apple Watch, AirPods, and Beats products. We do know that wearables achieved $10 billion in revenue for the four quarters leading up to Apple's fiscal 2018 third quarter. Expect to hear more from Apple on the subject.

Don't forget the reporting change

It's important to remember that CFO Luca Maestri said last quarter that, beginning with the December-ended quarter, the company would "no longer be providing unit sales data for iPhone, iPad and Mac." He went on to say that a unit of sale was less relevant than in the past, while also pointing out that top competitors in smartphones, tablets, and computers didn't provide quarterly sales data, either. 

Apple already released its preliminary results so there shouldn't be too many surprises. For the specific cases where the company didn't provide numbers, it left a trail of breadcrumbs to follow or hinted at the rest. One area that hasn't been addressed is Apple's guidance for the coming quarter -- which will be of keen interest to investors. Unfortunately, with the ongoing trade war between China and the U.S., I wouldn't hold out much hope for optimism, as it was softness in China that did the most damage during the first quarter, according to Cook's letter to shareholders.  

Stay tuned. We'll get the full report after market close on Jan. 29.

Check out the latest Apple earnings call transcript.