Conversion to Roth - why asked for all account values

I converted a single traditional IRA account to a single Roth account.

I entered the 1099-R information into Turbotax.

I get to the section "Tell us the Value of your Traditional IRA"

Here I am asked for the "total value of all" my IRA accounts on December 31, 2021.

Why does Turbotax need to know the value of ALL my IRA accounts, when only one account was converted?

Also, the traditional account was converted prior to 12/31/21 so what help is it to know the value on 12/31/21? Which would be zero.

Thanks.