JustBeingReal on 08 January 2016
I wouldn't personally take the figure as a confirmation of all XBox One's sold through to end users.
It depends entirely on how registering windows is done. If it's handled at the retail level, like all registrations are made when you buy your Xbox One, then yeah it's 18 million XBox One's sold through, but if registration requires all users to either contact Microsoft, by either logging on through their internet or sending off a registration that's in the box of their new system, then some people aren't going to have registered their system.
Still impossible to say just how many XBox One's have been sold to date without this issue being clarified, but I'd expect 18 million to be pretty close to the real number of sold through Xbox One's.
