Deductions & credits

I see through this exchange that you have calculated two different gains on sale. I'm not following along with the distinction between the two. Are both calculation or is it an either or situation.  

Part of the problem is that when clicking on help in web based program, it says the program won't be able to make the calculation if the % of use varied each year.  I was trying to plug numbers to approximate something very close to the business gain of 3,550.

In your second calculation covering the life of the vehicle the gain was on ly 2,031. Which do I use. The car was not converted back to personal use when it was no longer used for business.

Thank you.