Reporting part-time earnings while on benefits - 14 months and counting

I picked up part-time shifts as a school bus driver and I am confused about how to report them. There are 16 people counting on me, so I am trying to be careful. Sometimes my paycheck is late by a week. Do you report when you earned it or when you were paid?

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