HSA contributions that are shown in box 12 of your W-2 with code W are considered employer contributions, even though the money came out of your pay. The contributions shown with code W have already been deducted from the wages in box 1 of your W-2, so you are not paying tax on them. You cannot deduct them again on your tax return.
Stick to the Step-by-Step interview for entering your HSA information. Don't make entries in forms mode. TurboTax is handling it correctly.
