Told I owe money back on my benefits - 10 months and counting

The agency says I reported earnings incorrectly, but I think I followed the instructions. I worked as an IT help-desk technician before this. The letter mentions an appeal window and a repayment plan. 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.