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

I picked up part-time shifts as a procurement assistant and I am confused about how to report them. There are 8 people counting on me, so I am trying to be careful. Sometimes my paycheck is late by a week. Did anyone get an overpayment notice from a mistake?

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