You do not need to explain your choice of credit over deduction. You have the right to choose the more beneficial method.
If the repayment is $3,000 or less, it is a miscellaneous itemized deduction and can longer be deducted.
If the repayment exceeds $3,000, you can only report it in the year you actually repaid the claim.
There are a couple of ways to get a tax break by reporting the repayment in the year of repayment:
Please read this TurboTax Help topic for more information.