My Roth IRA contribution is being deducted from the amount of my conversion from a traditional to Roth IRA

I am converting $15,000 of a traditional deductible IRA to a Roth IRA. I am also making a $5,000 contribution to my Roth IRA.  Turbotax is reducing the taxable amount of my conversion by the contribution amount. Why is that happening when the Roth IRA contribution should not be deductible?