yes it is. for a single person once taxable income goes above 182100 for 2023 the Qbi deduction is phased out (or the way the Congress/IRS tells it the reduction is phased-in)
and would be completely gone if your table income was 232100
you have excess taxable income of 46231 (228331-182100)
that's about 92.46% of 50000 (the range above 182100 in taxable income where the QBI deduction is phased out (or as Congress and the IRS put it the reduction is phased-in)
so your tentative QBI of 51844 (259221 x 20%)
is reduced by 92.46 % or 47935
so the remaining QBI would be 51844-47935 or 3909. the small difference is that 92.46% rather than 92.50% is used (4 decimal places)
so the more your taxable income is above 182100 (at least for 2023 since this amount changes every year) the smaller the QBI deduction gets
the sad part is that if you were married with the same numbers you would have gotten the full 51844. that's because for a married individual the phase-out starts at 364200 and wouldn't be completely eliminated until taxable income reached 464200 for 2023
