Overpayment letter from the unemployment office - what worked for you?

The agency says I reported earnings incorrectly, but I think I followed the instructions. It has been weighing on me all week. The letter mentions an appeal window and a repayment plan. Are payment plans possible?

Thanks for writing this out. I went through something close to it 6 months ago, and it settled down once I kept a simple log of every call and form.