How is Immortal Hulk's bonus attack rating calculated?

I have been looking at Immortal Hulk's kit and one aspect is that "Gain up to (X) Attack Rating based on how much health Hulk has lost during the entire fight. This ability is based on 200% of Hulk’s Health."
I may just be dumb but how exactly is this calculated during a fight?
I may just be dumb but how exactly is this calculated during a fight?
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But sounds like the “based on 200% health” is because it could factor in any Regen done during fight (either from Regen of any Recoil damage, or post Invulnerability).
Not just looking at the current state of his Health Meter for determining the increase in Attack Rating,