Overpayment letter from the unemployment office - first time posting

After 12 weeks of benefits I got a notice saying I must repay some of it. Any experience at all would help. I cannot afford to repay it all at once. Has anyone disputed one of these?

Collect your pay stubs and certification records for the weeks they name. Mine showed the error was a date mix-up.

Thanks for writing this out. I went through something close to it 12 months ago, and it settled down once I kept a simple log of every call and form.