umm, the ps3 has outsold the 360 for the past couple of months according to your charts and yet the 360 lead has grown from 3.3 to 3.4.  something obviously isnt adding up.

This should go in sales for future reference. There were adjustments.

old adjustments

Adjustments....because the PS3 wasn't outselling the 360 as much as what the previous charts showed.

As others have said, it was adjustments

More detail

VGChartz base their data mostly off a limited selection of retailers. Only the high ups here know what percentage it is, but 5% wouldn't be a bad guess for the USA/UK/Japan. The staff here use this data to make estimates as to what the total sales are.The data in which the PS3 was outselling the 360 were these estimates.

Later on, additional data comes in. This comes under two broad categories - manufacturer shipment figures and other sales tracking companies. Based on this data, VGChartz then adjusts their predictions, in order that we have the most accurate old data of any of the tracking firms, even though we have a smaller sample size than some of the bigger tracking firms.