The amount of taxes withheld from your 1099-R was only an estimate, no different than taxes withheld from your paycheck. You enter the information from your 1099-R exactly as it is on your form, including the tax that was withheld. The amount of the distribution is added to your other income and taxed at whatever your marginal tax rate is. The actual tax could be more or less than what was withheld. In addition, if you were under 59 1/2 when the withdrawal was made, you have to pay an additional 10% penalty for early withdrawal. You get full credit for any tax that was withheld, so the Turbotax calculations are accurate.
