ok makes sense if the $1 was carried forward as basis from prior year it was some earnings from prior year you already paid tax on it.
yes the 12/31 is only referring to Traditional IRA(s) not Roths - see 8606 instructions for Line 6 - if you've moved everything to Roth then you're in good shape for backdoors
https://www.irs.gov/pub/irs-pdf/i8606.pdf
