TurboTax is doing this correctly, and if you made an entry on line 7a it probably should not have been made.
See page 17 : https://www.ksrevenue.org/pdf/ip18.pdf
LINE A7:
If the amount on Line 1 of Form K-40 is $75,000 or less, enter the amount received as benefits in 2018 under the Social
Security Act (including SSI) to the extent these benefits are included in your federal AGI.
Do not make an entry if your social security benefit is not subject to federal income tax.