20K converted fr 403B to Roth IRA. 1099R shows taxable 20K, code "G". T-Tax shows 0 taxable, and also on line 16 "Pension" (wrong), not on line 15 "Reti" (right). Pls adv

I converted 20K from 403b to a Roth IRA acct in 2017. Got 1099R form (from Prudential hosting 403b, hard copy), showing 20K in box 1 "total distribution" , 20K in box 2a "taxable amount", and code "G".  When the info is entered in 1040 on line 15 "Retirement Plan.." (via the underlying 1099-R form),  line 15 becomes blank, and line 16 (Pension/Annuity) shows 20K, and 16a "Taxable amount" shows "0"!

I suspected the code is wrong, but Prudential says "G" is correct for this transaction.

I understand the 20K is taxable, and I expect to see info on line 15. 

Pls clarify and advise on how to resolve the issue. 

Thanks