Deductions & credits

I have a bit of a unique problem and I am trying to solve it.  I have talked to three Turbo Tax experts online, and none of them could help solve my problem.  I sold my old car on 8/24.  I am an independent contractor who uses a personal vehicle less than 50% of the time for business.  I have always taken the standard deduction for mileage and I have never used form 179 to depreciate the vehicle in any year.  As I am itemizing my expenses for schedule C, for my vehicle expenses, I am being asked to detail the information about the car I am taking out of service.  The dealership offered me $500 for my old car.  I used it 24.71% in 2020, meaning $124 applied as a business gain, which I entered.  Then, I get taken to a screen that asks me about "vehicle Cost".  I am assuming this was the original cost of the vehicle, when I bought it in 2008, so I entered that cost of $35000.  I then got a screen to determine basis of loss/gain.  I originally bought this car for $35000, and traded in a car that was worth $23000 (new in 2003), so I list my gain as $12000.  The next screen asks me for my prior depreciation equivalent, which is $31116.  The next screen tells me that my Gain on Sale is $124.  When I go to my main page of income and expenses, it lists the "Sale of Business Property" as $5808.  Nobody can tell me why that number is popping as income, and nobody can tell me what I am entering wrong.  Can you help?