How do you report hours that vary week to week? (update)

I picked up part-time shifts as a quality inspector and I am confused about how to report them. This is my first time dealing with any of this. The form asks for gross earnings, which I do not see until later. Do you report when you earned it or when you were paid?

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