Does DD on box 12 of my W2 represent my employer's contributions to my HSA?

The amount corresponding to Code DD in Box 12 of your Form W-2 is the total cost of what you and your employer paid for your employer-sponsored health coverage plan.

Enter Code DD and the corresponding amount exactly as you see it when you're entering your W-2.

Please see the TurboTax Help article What is code DD in Box 12 of my W-2? for more information.

And code DD does not represent your HSA contributions.  HSA contributions made through your employer are reported in box 12 with code W.