Reporting part-time earnings while on benefits - any advice?

My hours change every week at my new part-time job and I am afraid of reporting wrongly. I have read a lot of threads here and could not find my exact situation. Pay posts on a different day from when I work. 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.

I estimated and then checked my pay stub. When there was a small difference I wrote to the agency to correct it.