You can see when you reached zero the STATUS.Z reflected that. However, you alter the STATUS Register in your code. About the only thing you can change is the C bit. Delete the "status=1" line and try again.
your assertion is
If subtracting and want to see if it rolled from 0 to 255, "STATUS.C = 0". Look in your data sheet for the STATUS Register and how it works.

You don't state what PIC this is for, so I randomly grabbed the data sheet for a PIC16F1824; STATUS Register 3-1, page 24.
if your assertion was correct it would not matter but its a12f1840

i repeat
mike would you like to provide some pbp code that demonstrates use of status register following pbp addition or subtraction
for any chip