Overpayment letter from the unemployment office (update)

I received a letter saying I was overpaid about $950 on my claim. There are 14 people counting on me, so I am trying to be careful. The letter mentions an appeal window and a repayment plan. Has anyone disputed one of these?

Collect your pay stubs and certification records for the weeks they name. Mine showed the error was a date mix-up.

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.