What rocketpig said.
However, vaguely on topic: I don't believe that Microsoft (or Nintendo or Sony) has a 100% accurate way to measure the sold-to-customer amounts of a given console. They probably have access to more data than VGChartz does, but, unless they spent a rather large amount of money tracking down the sales data of every store that sold their consoles, they too would have a margin of error.
It also occurred to me that because of how sales work for video games, a majorly hyped title can bomb and the creators can still get most of their money back. The store owners have to foot a large part of the bill if only a low percentage of shipments sell.







