While we can’t verify those numbers independently, Blizzard says they’re based on internal company records and information from distribution partners.
Cataclysm, the third expansion to Blizzard’s World of Warcraft online roleplaying game, shipped in early December to dozens of countries and was available in advance of retail copies for online, download-exclusive purchase.
Though not specified in the presser, I’m assuming Blizzard counts pre-sales as well as “day-of” sales. Those of us who purchased and downloaded the essential game code weeks in advance are presumably umbrellaed in that 4.7 million figure.
What’s missing from the presser are updated subscriber numbers (last we heard, the figure was 12 million global players). Blizzard’s presser doesn’t include them, meaning one of two things: They’re low, i.e. the lion’s share of Cataclysm’s sales were to existing players, or the company’s looking to spread coverage by shunting subscriber data into its own presser.