This specific scenario isn’t addressed in the regulation or commentary. However, based on comment 10034(a)(7)-3 states:
“Covered loan amount—preapproval request denied, application denied, closed for incompleteness or withdrawn. For a preapproval request that was denied, and for an application that was denied, closed for incompleteness, or withdrawn, a financial institution reports the amount for which the applicant applied.
Its seems as though the applicant requested/applied for $150,000 and that is the amount you were using for underwriting. I think that is what you would report.