This is almost certainly interest that accrued on a federal income tax refund that you received late from the IRS. See the IRS's Interest for Individuals page for more information.
You'll need to enter information from this form into TurboTax manually, and don’t enter anything in the Box 3 field. Just enter Box 1.
Please see the TurboTax Help article Where do I enter Form 1099-INT? for guidance.
