Overpayment letter from the unemployment office after 7 years as a teaching assistant

The agency says I reported earnings incorrectly, but I think I followed the instructions. It has been a long 5 weeks. The letter mentions an appeal window and a repayment plan. Has anyone disputed one of these?

Thanks for writing this out. I went through something close to it 7 months ago, and it settled down once I kept a simple log of every call and form.