wingnut has it right. It doesn' t work out to 309, 307.
TJ, you seem to be counting 11' s as 1 point bonuses. There is no " bonus," just an 11, 10 8, 5, and 0.
You stated, " 29 - 10' s and nine of those were 11' s." Well, it was actually 20 - 10' s and 9 - 11' s.
New2, subtracting is just a different way of keeping score. For example, if your at the first of 30 targets and you shoot an 8, you score is now 327. At the next target, you shoot a 5, your score is now 322; the next target you shoot 11, your score remains 322, etc.
It' s just like shooting an indoor 300 round: every time you shoot a 4 you subtract one from 300.