In all of EA reports(that I can find) ME2 sales figures are not listed. So if you could link the report you are seeing, that would be good.
EA 4th qtr PDF
EA profits
EA Sees Q4 Profit Sales Up 14 Percent.php
In fact the only sales data I can find:
1UP: 2 week sales
VG Zero: 178,737 (975,537) in 7 days
Gamespot: 572,100 in 5 days
GamersShell
LazyGamer: Mass Effect 2 Outsells Everything Else by at Least 6-1
january npd sales numbers are in mass effect 2 kills
aussie charts mass effect 2 triumphan
mass effect 2- ops uk sales char
Then there is this:
From joystiq which is the first place besides Vgchartz and Wikipedia(which was dated March 31, two months after the release) for me to see the 1.6mil figure.
Of course we could take this 6.6 million-selling sequel Mass Effect 2 figure as truth.(You would of thought the site would of corrected the error by now)