… For premium players!
You would have previously downloaded a ~6gigabyte patch, which is now accompanied by a 4.2 Gig update. To make sense of it, it appears the second update contains just the maps. .The previous 6 gig update patches previously existing content in the game, which means two gig is added in total (plus whatever the result is from this second update..)
If this is the final update for Battlefield 3, we may have the largest game ever made – It will come in at approx 36 Gigabytes, installed. Impressive!
To help you get pumped while downloading like I am, check out this amazing footage of midair motorcycle RPG action: