As far as I can tell, using Form W-4P and leaving Step 2 blank will result in tax withholding equal to the expected tax liability as if your distribution from the corresponding account plus one-half of the standard deduction for your filing status is the only income being reported on your tax return. Any amount that you specify on Form W-4P line 4(c) is an additional amount of withholding beyond that. For example, if you file as Single for 2023 and leave Step 2 blank, withholding on an annual periodic payment of $30,000 would be $2,750 plus whatever amount you specify on line 4(c). See Worksheet 1B of IRS Pub 15-T for details: https://www.irs.gov/pub/irs-pdf/p15t.pdf
