I'm not sure exactly what you want to change, but it's all in buffs.xml.
You might want to look at buffInjuryBleedingZombie which is what adds bleed counters to zombies.
A bit further down is buffInjuryBleeding, it's what runs the HealthMaxModifierOT and HealthChangeOT effects for things with bleed counters.
It has a duration of 20, and a stack type of replace, so the duration refreshes every time an entity gets hit with a bleed weapon.
Basically the bleed amount is equal to the bleed counter, so with 5 stacks things take 5 damage per update.
If you want to weaken it the easiest way is to just reduce the duration, alternatively you could reduce the maximum stacks (or both).
It'd be a lot trickier to make it give less than 1:1 damage per counter, but you could just do multiple operations.
IE the original set is this:
Code:
<triggered_effect trigger="onSelfBuffUpdate" action="ModifyCVar" cvar="$bleedAmount" operation="set" value="@bleedCounter"/>
If you wanted it to do 2/3rds damage per stack you could try something like this:
Code:
<triggered_effect trigger="onSelfBuffUpdate" action="ModifyCVar" cvar="$bleedAmount" operation="set" value="@bleedCounter"/>
<triggered_effect trigger="onSelfBuffUpdate" action="ModifyCVar" cvar="$bleedAmount" operation="multiply" value="3">
<triggered_effect trigger="onSelfBuffUpdate" action="ModifyCVar" cvar="$bleedAmount" operation="divide" value="2">
It might have weird rounding issues though, since I'm not sure if $bleedAmount is a float or an integer (decimal or whole number).
If you have some specific thing you wanted I can probably make you a modlet for it, unless you want to do it yourself.