Yes this is a bug that slipped by because we never tested with 1 round = 1 map *blush* and no one whipped out a calculator summing up their scores and comparing over 3-4 rounds.
What happens is, the game logic adds your round scores to your match scores every time the logic enters the DELAY state. So when the match ends, it enters the delay state for the round, then AGAIN for the match only this time with a "Final" flag being set. So it's adding your previous rounds scores twice.
Not a terrible bug since it is all for fun, but it could screw some final rankings if you did poorly your final round compared to your others. This is already fixed and ready for the B3 patch.
This fix will also make it so that for 1 round = 1 map servers only the MATCH scores show and not the round (with a delay of ge_rounddelay + mp_chattime). That way you don't have two scores popping up that say the same thing. Again, sorry!
BTW, you can get by with a roundtime of 21*60 seconds instead of 3 hours, it just clamps to the map time