How does the generic CC's "use when low health" work

[Poofie]

Currently im trying to figuere out how this particular setting is working. First i tried adding 65, thinking it would be % based, that didnt work. Then i tried to add 10000 hp on my 13k hp barb, but it still decided to use it on 100 % hp even before getting into combat with the mobs..

Anyone who could help me so i can tweak the cc better for my liking :>

[Tony]

its a percantage not HP