Roth conversion on 12/31 taxable on Form 8066?

I attempted to do a backdoor Roth conversion ($6k from Traditional IRA) prior to 12/31, but the actual conversion was executed on 12/31. Form 8066 asks on Line 6 asks if I had any balance in my traditional IRA
"as of December 31?" I guess technically at the start of the day on 12/31 I had $6k, but after the conversion and at the end of the day it was 0. How does this language work in terms of having a zero balance in my Traditional IRA by the end of the year?