Apple reports how many devices that they actually SELL to the end user.
That is one of the biggest myths repeated on the internet. As any real Apple follower knows:
APPLE REPORTS SALES TO RETAILERS, IN ADDITION TO THEIR OWN STORE SALES TO END USERS.
In fact, Apple reports a sale the moment a unit ships to a retailer. (Returns are accounted for separately.)
Samsung (and others) keep reporting what they SHIP not what was actually SOLD to the end user Why? This skews public perception into thinking that their products are in much higher demand than they actually are.
The same thing sometimes happens with Apple.
Such overly optimistic retail buying is exactly what happened with Apple's sales reports TWICE this year so far, as pointed out in their quarterly calls. The two cases this year so far were:
Sales of iPhones dropped off almost 3 million between the first and second calendar quarters and Apple was asked what happened. Cook responded that sell-in to retail stores was larger than the sell-through to end users in the first quarter, and thus stores bought fewer phones the next quarter, as they had about a million and a half extra sitting on their shelves already.
Again, in the most recent quarterly call, Cook explained a similar drop in iPad sales using the same reason: stores had overbought inventory.
TL;DR - Apple also reports shipments to stores. Apple also runs into the situation where sell-through is less than sell-in to retailers, which makes their sales figures look extra good one quarter, and extra bad the next.