That's ok for 4a. As long as the taxable amount is right on line 4b. If the taxable amount on 4b is the same as the gross distribution on 1099R box 1 then it doesn't show the amount on 4a.
See IRS Pub 590b page 22
https://www.irs.gov/pub/irs-pdf/p590b.pdf
Reporting taxable distributions on your return. Report fully taxable distributions, including early distributions, on Form 1040, 1040-SR, or 1040-NR, line 4b (no entry is required on line 4a). If only part of the distribution is taxable, enter the total amount on Form 1040, 1040-SR, or 1040-NR, line 4a, and enter the taxable part on Form 1040, 1040-SR, or 1040-NR, line 4b.
