BF2S Forums How did I just unlock that?

Hey everyone...I was playing SF and regular BF2 the other day...I was going for Gunnery Sergeant on and I got it while playing BF2...but I got 2 free unlocks...I thought you only got 1 unlock per promotion. However that's not the weirdest thing...that same night I was just doing some single player trying to get some familiarization time with the SVD since I normally only use the M95...and I went through maybe 4 to 5 rounds of it on Surge and Mass Destruction with over 100 pts. each time...keep in mind it was on easy and it was single player...with the vast majority of my kills being head shots which I was pleased with...but once again...easy mode...anyway I back out and disconnect and much to my surprise I get 2 new unlocks!!! And I haven't been online since I got promoted and unlocked the previous 2!!! So in the course of 1 day I got 4 unlocks...and no I don't hack or cheat...I'm too stupid and lazy to do that...I was wondering if anyone out there might have a clue as to why I got my 2 last unlocks...I'm not complaining but I'm really curious as to why this happened...thanks...