See pages 17 & 18 (pdf pages 71 & 72) in the 2022 GIR.
Enter, in dollars, the gross annual income relied on in making the credit
decision, or if a credit decision was not made, the gross annual income
relied on in processing the application. Round all dollar amounts to the
nearest thousand (round $500 up to the next $1,000).
Example: If the income amount is $35,500, enter 36.
In this case you relied on $4000 per month in processing the application. That is the income you report.
The opinions expressed are mine and they are not to be taken as legal advice.