How does Deep Wounds, the passive, work?

https://imgur.com/Aizwh1x


Hypothetically, if my bleed duration is 4 seconds, does that mean that this passive never works? I am wondering if it only aggravates singular instances of bleed which are over 4 seconds, or does it require the target to have been continiously bleeding for over 4 seconds and then you just aggravate any bleeding on them?