Tesla left out a critical piece of information in its 2017 guidance

Tesla reported fourth-quarter earnings on Wednesday, and after posting a profit for the third quarter, the automaker went back to losing money in Q4 - although it lost less than analysts had expected.

What was interesting about Tesla's investor letter this time around was the notable departure from providing guidance on vehicle deliveries for the coming year.

Last year, Tesla guided to 80,000-90,000 deliveries and fell short, getting only about 75,000 vehicles into customers' hands.

For 2017, the company said that it would "deliver 47,000 to 50,000 Model S and Model X vehicles combined in the first half of 2017, representing vehicle delivery growth of 61% to 71% compared with the same period last year. In addition, both GAAP and non-GAAP."

Tesla also said that it expects to be producing 5,000 of its forthcoming Model 3 mass-market vehicle "at some point in the fourth quarter and 10,000 vehicles per week at some point in 2018."

A little back-of-the-envelope calculation suggests that Tesla should deliver something like 150,000 vehicles in 2017, if it can make those numbers.

This means that Tesla will require a significant increase in deliveries to meet CEO Elon Musk's pledge to deliver 500,000 vehicles annually by 2018.

Tesla didn't immediately respond to requests for a comment on its deliveries guidance.

But after softly rolling back guidance in 2016, when the 80-90,000 vehicles for the full year became 50,000 for the second half, Tesla appears to be preemptively dialing back on its ambitious deliveries targets ahead of the Model 3 launch.

However, if taking a breather on Musk's guidance goals means Tesla will launch the Model 3 on schedule, investors may reward the company's caginess on deliveries. Tesla shares were trading up after hours, about 2% to $278.