How do you report hours that vary week to week?

I picked up part-time shifts as a retail manager and I am confused about how to report them. I have been trying to stay organised about it. The form asks for gross earnings, which I do not see until later.

Thanks for writing this out. I went through something close to it 3 months ago, and it settled down once I kept a simple log of every call and form.

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