Reducing damage of an EntityDamageEvent allows future damage to bypass NoDamageTicks partially

Expected behavior

This issue applies to all damage types, but is specifically more noticeable in damage types that attempt to deal damage each tick (lava, cactus), so i will use lava as an example.

When standing in lava, I expect armor to take damage every 10 ticks as it does in vanilla, regardless of the amount of damage the lava deals.

Observed/Actual behavior

Armor takes damage and lava burn sounds are played every tick.

Steps/models to reproduce

1. Create a plugin with the following handler in a Listener:
   @EventHandler
public void onLava(EntityDamageEvent event) {
if (event.getCause() == EntityDamageEvent.DamageCause.LAVA) {
event.setDamage(event.getDamage() * .99);
}
}
2. Run the server and equip armor.
3. Stand in lava.
4. Observe your armor taking damage each tick, instead of every 10th tick.

Plugin and Datapack List

Nothing except this listener.

Paper version

This server is running Silvera version 1.21.1-DEV-main@9d0a210 (2024-09-13T02:50:33Z) (Implementing API version 1.21.1-R0.1-SNAPSHOT)

This is a private fork, but is based off of latest and has no related changes, several other servers have run into this issue, presumably on other forks or standard Paper. I can replicate it on latest if necessary.

Other

This appears to be the source of the issue. https://github.com/PaperMC/Paper/pull/11045/commits/d98db3945a76eb6203062c7ccfa2a71bce22f4e4

This is caused by amount being set to a lower value before lastHurt is assigned to this value.
For example, lava deals 4 damage, but if this is reduced to 3 damage, lastHurt will be 3 on the next tick, but amount will be 4, resulting in the if case failing and damage attempting to be dealt.

Start by examining the linked Paper pull request commit and reproduce the issue with the minimal EntityDamageEvent listener described here. Trace how reduced damage is compared with the entity's existing damage cooldown, then verify that lava damage, armor wear, and burn sounds are throttled to the vanilla interval after damage is reduced.