jaybird561: why do you not get full Xp credits for how you played up to the point when they quit?
How should we answer the "Why?" question?
Anyway: You get points considering the game's final.
That is, 1 XP at once for every shot and whatever points are due for the game on finalisation. If you finish single, you get XPs for single play. If you don't finish, you get none.