Neither TurboTax nor your tax return classifies an RMD as applying to any particular year. Your tax return simply reports distributions. Any RMD (or any other regular distribution) received in 2019 is taxable on your 2019 tax return, regardless of the year for which the RMD was taken.
If you somehow mistakenly reported this distribution on your 2018 tax return, amend your 2018 tax return to remove it.
