Hitpoints of Enemies not reduced properly

Platform: PC

Do you have any mods?
Arcemi Pathfinder Savegame editor
Please explain the issue is in as much detail as possible:

Hey, I’m not sure if this is a bug or if I’m just stupid and don’t understand how it works, but as you can see in the picture below I already dealt some damage to Derakni Devastator but the enemies Hitpoint list still shows 415/415. It only starts to count down after first or second round. Am I missing something?

These are temporary hit points - from barbarian rage, in this case.