the source is a chinese site but with charts from china, japan, taiwan, korea and others. If it's true I think is the total of all these asian countries, but it's not
As far as I know it's legal downloads in China only (but they seem to have a weird system where they count all the track downloads together and then you have the album sales?? Maybe I'm confused with another site, but anyway), but most people don't count them because they're extremely cheap (like, less than a $ per album, because it's the only way to combat piracy there).
Btw it's her 2nd best selling album (pure sales) in the US, right? 6M is huge, last I checked she was still at 4M (2 years ago?