On a 1099-R form:
Boxes 14,15,16 can have multiple lines....so the first line is considered 14a, 15a, 16a, and if there happens to be a second state line...it is considered 14b, 15b, 16b.
For NY, NY residents have had issues with that every year. Box 16 must have a number in it.
1) IF box 2a has a value in it, put that in box 16.
2a) IF box 2a is empty, or undetermined, use box 1 instead if all of box 1 is Federally taxable.
2b) If box 2a is empty and IF a portion of the distribution shown in box 1 came from after-tax contributions to that retirement fund, then the Federally-taxable portion of box 1 is entered into box 16.