It's possible, but it may be part of the refund you've already received.
It could also be a mistake. If you also see a Transaction Code 767 with the same amount in the same vicinity of your transcript, it means the credit was reversed.
According to Section 8A, Master File Codes - Transaction, MF and IDRS Collection Status, Freeze and IDRS Status 48, Restrictive and Filing Requirements in Document 6209 - ADP and IDRS Information, transaction code 766 is:
[A] refundable credit (other than ES or excess FICA) which was verified on a Form 720, (abstract 11 amount) 941, 942, 943, 945 (Advanced Earned Income Credit) 990C, 990PF, 990T, 1040, 1040C, 1041, 1120 or 1120S return but not previously posted to the Tax Module, or from the appropriate line item adjustment of an Examination or DP Tax Adjustment. Includes credit allowed for gasoline tax paid, credit from Regulated Investment Co., or Covenant Bonds with item reference 334 (199312-199411 only) for installments of 1993 additional taxes. See Section 8C.3.
Note: TC 766 with CRNs 946 and 966 are refundable credits. These CRNS are reimbursements of the Installment Agreement user fee due to the Bipartisan Budget Act of 2018, Section 41105 and the implementation of the legislative requirements that impacted IA's entered into on or after April 10, 2018.
