Hey Andrew, it looks like you may be misinterpreting the scoring rules in some way. I'm not sure where the discrepancy is, but maybe using an interface that scores as you go along will help you out a bit. Here's one who's scoring I know to be congruent with the rules in the kata:

http://www.bowlinggenius.com/

If you still run into trouble, or if you figure out what was confusing, let me know and we can work on updating the kata instructions to be clearer! :)