So, here's what happened.
I skip my turn for other reasons...

Backstabs runs 40 feet closer to the archer, and throws her knife at his leg.
Backstabs' roll: 10 (+9) = 19
Archer's dodge roll: 2 (+16) = 18

She hits, dealing...
5 (+9) = 14 - 10 = 4 + 2 = 6 damage

Ranger's HP: 7/15

...
+ Leg injury (Half AGI and LUCK until properly healed.)
Human's Luck: 31/2 (rounded down) = 15
Ranger's LUCKmod: 8

Human's AGI: 29/2 (rounded down) = 14
Ranger's AGImod: 7