Code DD in box 12 of the W-2 has nothing to do with retirement contributions. It reports the cost of employer-sponsored health insurance.
Enter amounts shown in box 12 of the W-2 only in box 12 of TurboTax's W-2 form, nowhere else in TurboTax. Nothing on a W-2 is to be entered under Deductions & Credits
Amounts reported in box 12 with codes D and AA show contributions to a 401(k) plan not to any kind of IRA.
