A trade secret for ProConnect Tax is that zero is worthless on it's own. It is a simple NOTHING. If you would like the $800 to become a zero, then 0 does not do the job. The magic bullet is the -1, which is the zero of ProConnect. Go forth and annihilate the $800 with and override of the TRUE ZERO.

But where? It's difficult to find.

2nd trade secret - How to find input

Check return > find the form you want to inquire about > look for the troubling line or box  > If it is shaded blue,

Click on it and VOILA! There she is!!! The input box!!!

Short answer to your question - You cannot change that autofill. This is verified by the input your finally found that says defaults to $800