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. Thank you in advance. The form asks for gross earnings, which I do not see until later. Did anyone get an overpayment notice from a mistake?

Thanks for writing this out. I went through something close to it 5 months ago, and it settled down once I kept a simple log of every call and form.