I'm all clear now. Thanks!

My original question was confusing - it is a 2017 1099-R with a code "P" to be reported on a 2016 tax return.

To confirm, I was issued a 2017 1099-R for "Return of contribution taxable in 2016".

Therefore, TurboTax assumes the 1099-R is for 2016 so code "P" states "P-Return of contribution taxable in 2015". However, TurboTax asks on one of the following...