It helped that Microsoft only shipped 1million units in those 6 months...
Really though with PS3 numbers something is missing and we will see if ioi or PS3 fans are correct once SONY's q1 shipment numbers comes in. IF SONY ships the ~2.5 million consoles they need to make there 13 million prediction, then its obvious that PS3 is undertracked, if SONY ships ~800k-1million units then ioi was right with these adjustments. (Though the 3 million gap in sales/shipments through 31st december is kinda big)
In other words PS3 sales by 07th Feb 2010 could be over 33.2M, which would make PS3/360 GAP below 4.8M by now.
The end of September ship totals were 33.5m for x360. VGC x360 sales for Oct 03 - 32,101,684.
The end of December ship totals for PS3 are 33.5m. VGC PS3 sales for Jan 02 - 30,576,218.
And there were some shortages for 120gb PS3 model in NA during January.
Just for the records, Sony didn`t changed their projections for fiscal year 13m, http://www.scei.co.jp/corporate/data/bizdataps3_sale_e.html - they already shipped 10.8m and planning to ship another 2.2m by the end of March 2010. That will make around 35.7-36m by the end of March.