Gears of War 2 Annex XP Questions!?!?

When Im playing Annex online, I feel like I dont get all my XP. Because at the end of the game it will show you the XP you just earned in that little bar at the bottom. But That bar at the bottom always shows less than what it says in my game score. Does it only give you the XP that you got in the last round of Annex? Please help me out because its a 21x score multiplier right now. Thanks!