The "BLUS31011 DLC PKG" refers to a specific digital content package for the North American version of Call of Duty: Black Ops II on the PlayStation 3.
: Your game’s Title ID must match the DLC’s ID. If you have the BLUS31011 game, you must use BLUS or NPUB (digital) DLCs. Using European BLES files with a US BLUS game will result in the content not appearing. Blus31011 Dlc Pkg