Reporting part-time earnings while on benefits - 23 weeks in

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?

Keep everything in writing and save the confirmation numbers. It made the follow-up calls so much easier.