Once per Combat or Once per Combat Round?

Currently playing Raiders and I’m confused by wording on special abilities. Can I use the modifiers once per combat round (meaning multiple times during combat) or once per combat entirely? So for example with iron will, can I increase my armor during each combat round, essentially meaning throughout combat or can I only choose one round for the entire combat? The rules say per round, however I’ve also seen Q&A answers as only once per combat. It entirely changes the difficulty so I wanted to get clarity.