Which is why I asked. If you're going to use one source, it's never going to be the same as the others 100 percent of the time, so if something like this week happens you just have to stick with the primary source being used for this little competition. Honestly I figured they'd be using Media Create but VGchartz is fine. They had PS3 higher than Media Create did a few weeks back by a few thousand so it will even out in the end I'm sure.
Edit-Looking back it seems like ioi did change some older numbers, as I'm sure VGchartz had Wii over PS3 the second week of the Wii's price drop and now it's not.