Overpayment letter from the unemployment office after 8 years as a welding apprentice

The agency says I reported earnings incorrectly, but I think I followed the instructions. I would rather hear the honest version than the polite one. The letter mentions an appeal window and a repayment plan. Who should I talk to first?

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.