About Potential Status [ 5% chance to ignore 20% / 40% Damage when attacked ] ?

I believe its :

5% chance to ignore 40% Damage when attacked
5% chance to ignore 40% Damage when attacked
5% chance to ignore 40% Damage when attacked

With this i mean that the skill would proc individually so there is no 15% chance or 120% (I seriously doubt it, i think it would stack multiplicative instead of additive) unless the 3 instances procs at the same hit... And knowing nexon its most likely that you could only have one of these proc at a time or something.

My best guess would be the following:

If you were to have 3 lines of that potential, this will happen:
Maple checks if the 5% of the first line is hit. If it is, 40% dmg is ignored, and it stops there. If it isn't, maple will check if the 2nd line is hit, again, the same for the 3rd.
That means there would be an 0.05+0.95*0.05+0.95*0.95*0.05=0.1426 = 14.26% chance it will work, and you will ignore 40% of damage.