Retirement tax questions

I followed the steps you mentioned, TurboTax said "Fill out the form 1099-R on the next screen as accurately as possible. Later we will have you complete the required explanation statement on form 4852". I went to the next screen and entered the payer information and Gross distribution on 1099-R and now it's not letting me go further without selecting a code for Box 7 (picture below). Any help is appreciated. Thanks.