this comes from MS(Aaron greenberg) and it's upto today(the news is for today)
MS says the data is sell-through(to customers) and it comes from :NPD,chart track ,gfk,....
so why do we have 6.4 million here?remmember MS is saying 5 million more sold to the customers(casue GFK,NPD,... all record sold to customers)
http://www.destructoid.com/exclusive-destructoid-interview-microsoft-s-aaron-greenberg-on-gta-iv-85192.phtml#comments
"Today Xbox 360 has a 5-million-unit console sales lead on a global basis based on most recently public reported data from both companies. This includes more than double the installed base in the US according to actual NPD sell-through and over a 1-million-unit lead across Europe also based on reported sell-through from Chart Track and GfK."