I suspect that the code 1 Form 1099-R is for a distribution of after-tax money from a traditional 401(k) account and this money was rolled over to a Roth IRA (part of a split distribution with the pre-tax money being directly rolled over to avoid mandatory tax withholding and the after-tax money being indirectly rolled over). Because it was all after tax (Box 5 = box 1 and box 2a = $0), this rollover was nontaxable.
As far as I can tell, when entered properly by indicating that the entire amount of this distribution was converted to Roth, TurboTax does not include this distribution on Form 8880 line 4. The test return that I prepared behaved properly in this respect.
