More than likely that is the interest paid by the IRS for the late federal tax refund.
IRS website for information - https://www.irs.gov/newsroom/irs-statement-on-interest-payments
Interest on individual 2019 refunds reflected on returns filed by July 15, 2020 will generally be paid from April 15, 2020 until the date of the refund. Interest payments may be received separately from the refund. By law, the interest rate on both overpayment and underpayment of tax is adjusted quarterly. The interest rate for the second quarter, ending on June 30, 2020, is 5% per year, compounded daily. The interest rate for the third quarter, ending September 30, 2020, is 3% per year, compounded daily.