Wage reporting when hours change weekly - any advice?

I picked up part-time shifts as a graphic designer and I am confused about how to report them. There are 9 people counting on me, so I am trying to be careful. The form asks for gross earnings, which I do not see until later. Who can I ask without risking my claim?

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

Keep everything in writing and save the confirmation numbers. It saved me later.