How do you report hours that vary week to week? after 18 years as a forklift operator

I work some days through a staffing agency while still certifying. I would rather hear the honest version than the polite one. The form asks for gross earnings, which I do not see until later. Did anyone get an overpayment notice from a mistake?

The claimant handbook has worked examples for part-time pay. Mine was clearer than the phone line.