Got an overpayment notice, what now?, production planner here

After 24 weeks of benefits I got a notice saying I must repay some of it. There are 18 people counting on me, so I am trying to be careful. I did not notice any errors at the time. Has anyone disputed one of these?

I asked for a waiver and a plan in the same call, and they gave me both forms. It was less scary than I expected.