Isn't the 9% over Fallout 3 a typo? As in, should've been 90% instead? FO3 sold 610k in its first month.
Callahan made a gymnastic for give these percentages:
"Adjusting for days within the data month, this was the best Fallout launch in the history of the franchise having sold over 70 percent more units than Fallout: New Vegas and 9 percent more units than Fallout 3."