Received the same letter and situation from Iowa. TurboTax listed the $ amount from W-2 box DD on line 18 Health Insurance Premium in the Step 6 Adjustments to Income section. Here's a link to the 2018 form which is identical to 2017 so you can see where the adjustment occurred: https://tax.iowa.gov/sites/files/idr/forms1/2018IA1040%2841001%29.pdf
This didn't occur in 2016 or 2018 - 0's were listed by the TurboTax program. Looks like there was an error with the program in 2017 as I didn't manually enter this amount.
