OK so my roll:

Me: 14 + 8 = 22

Him: 16 + 6 = 22

...

Rerolling both

Me: 10 + 8 = 18

Him: 8 + 6= 14

I hit

1d12 roll: 10
10 + 7 + 1d3 (3) = 20 damage, - 10 = 10 damage

43 HP -10 = 33 HP