"When damage is taken, receives damage reduction effective in the round that reduces all damage taken by 10% (up to 60%)."
My understanding goes that (and let's use example) if in round 1 you get hit, then from that moment you receive 10% damage reduction. However it works only until the end of round 1, and at the beginning of round 2 it disappears.
If you are hit in round 2 then again, only from that moment you receive 10% damage reduction. If in round 2 you are hit again, then you get another 10% reduction that stacks with previous one. And again at the end of the round all 20% reduction disappears.

And I'm not sure if "when damage is taken" means that you get reduction before or after damage is calculated.

All in all it sound shitty, and even if I had one, I think I wouldn't waste money to level it enough to check if it's worth anything.