Total distribution or taxable amt?

I get an annuity from the government. The distribution amount is not all taxable . I paid into this when working.  I have state taxes only taken out. 
When I input the information the bottom part and put my state taxes in  I don’t have a state distribution amt in box 16. Do I put the total or the amount taxable in that box. TT won’t let me move on . I checked last year and it was blank then too. Help!