How do you report hours that vary week to week? - what worked for you?

I picked up part-time shifts as an insurance claims processor and I am confused about how to report them. It has been weighing on me all week. The form asks for gross earnings, which I do not see until later. Did anyone get an overpayment notice from a mistake?

Report honestly and keep your stubs. An honest small error is much easier to fix than a missing report.