With regard to the question asked, it doesn't matter. Since TurboTax is asking how much was RMD, TurboTax knows that this individual reached age 70½ in 2018. Any distribution in 2018 is therefore RMD until the RMD is satisfied. (No mention was made of this being intended as a QCD which would require the individual to actually have reached age 70½).
Essentially none. TurboTax simply treats the amount that you indicate as RMD as an amount not eligible for rollover. Since you did not roll any of the distribution over, it doesn't matter how you answer this question.