Bowmaster's Armor Break

So Armor Break finally got fixed in EMS and I have maxed the skill. Though I see the effects of the skill clearly I am not sure how it works. I was wondering if anyone can explain me this with some math on a boss with lots of PDR (i.e. CPB 180%).

Skill description (Under Master Level 20):
Grants a chance while attacking to ignore enemy defenses by a small amount, and deals extra damage in proportion to enemy defense rate. Every time the effect does not trigger, the chance to trigger increases.

Skill description (Current Level 20):
When attacking, ignores enemy's defense by 50% at 10% chance and deals 100% of enemy's defense rate as additional damage. Stacks activation chance up to 10 times if effect does not trigger.

Questions:

• Does the 50% def ignore gets taken directly from the 180% Or 50% of what is left after my Ignore Def (80%)?
  
• What do they mean by 100% of enemy's defense rate? That CPB's 180% makes me hit 1.8 times what I normally hit?
  

Please illuminate me.
Thanks in advance

The latter, so as an additional 50% PDR source, you'll go from 80% to 90% multiplicative PDR.

It means 100% of their PDR will be dealt as additional damage, so for Chaos PB's 180% PDR, you'll deal 2.8x damage for one attack.

http://www.basilmarket.com/forum/2759329/5

Ah I see now, thank you.