"Surplus Calculation" on BRRRR Calculator

[George Smith]

Anyone know how the Surplus calculation ($37,300 in this case) is computed under "Downpayment"?

$45,000 PURCHASE PRICE

Purchase Closing Costs	$2,300.00
Estimated Repairs	$55,000.00
Total Project Cost	$102,300.00
After Repair Value	$130,000.00

Acquisition

Down Payment	$0 ($37300 surplus)
Loan Amount	$82,300.00
Loan Points/Fees	$0.00
Loan Interest Rate	9.000%
Monthly Interest	$617.25
Total Cash Needed At Purchase	$20,000.00

Thanks,

George