Reporting part-time earnings while on benefits - 3 weeks in

My hours change every week at my new part-time job and I am afraid of reporting wrongly. 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?

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