Reporting part-time earnings while on benefits - 6 months and counting

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?

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