Overpayment letter from the unemployment office

After 13 weeks of benefits I got a notice saying I must repay some of it. There are 16 people counting on me, so I am trying to be careful. I cannot afford to repay it all at once. Has anyone disputed one of these?

Thanks for writing this out. I went through something close to it 13 months ago, and it got easier once I kept a simple log of every call and form.