The $16,000 was NOT the amount of income tax you paid on the $40,000 bonus (and hence not the amount you will get back with the 2020 credit). It was only the additional withholding (FICA and estimated income tax) .
If you have download (not online) 2019 Turbotax, you can use it to calculate your credit. Simply reduce your income by $40K and compare the new refund (or balance due) amount to the old. Or, you can use this tool:
https://turbotax.intuit.com/tax-tools/calculators/taxcaster/?s=1
to recalculate your 2019 tax liability, without the $40K.
