Power Knock Back

How does it work?

I've been trying to understand it, mine is lvl 1, string says +2% but data on ultimate skill tables says "13% chance".
Is that a +13%? or a 13%.
If it is +, then at max it would mean 100% chance knock back?

Also, I've noticed that it only works on some monsters, or has wayy different chance on some monsters.
On CPQ, I kb trojans most of the time, but it's imposible to knock back King blocktopus.
It also looks like it's nearly impossible to kb a roid.... that makes me think, is there a level factor involved?

Thanks in advance.

For bowmen im assuming this question is for. It adds said % to the knockback chance on the bow. So say a bow has 55% KB on it, and you have PKB giving +15%, you have a total of 70% to knockback and push away a mob when using PKB.

For bowmen im assuming this question is for. It adds said % to the knockback chance on the bow. So say a bow has 55% KB on it, and you have PKB giving +15%, you have a total of 70% to knockback and push away a mob when using PKB.

But the info on UST says 70% at max, if that were +70%, it'd mean a bow with 55% would end with 135 (asuming 100%)...

Taking my lvl 1 example:
String says: +2%, my xbow has 45%, that'd make it 47% chance
but UST says 13%, that could mean that everytime I use it I have 13% chance of knocking back 2 monsters, or 58% chance...

I believe its + Whatever % value is in the UST.

The string has been wrong for a long, long time.