How do you report hours that vary week to week? - any advice?

I picked up part-time shifts as a school bus driver and I am confused about how to report them. I do not usually post, so bear with me. 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?

In my state the question was about the week I worked, not the week I was paid. Read the wording on your form carefully, or ask the claims line.