When you filed your tax return, you had not yet received the second stimulus payment, so you claimed the Recovery Rebate Credit for that amount, and then subesequently received the stimulus payment. If you were due a refund on your tax return, the IRS will probably reduce your refund by that amount. If your refund is less than the amount of the stimulus, or you owed on your return, then the IRS will send you a bill for the additional tax you owe.