Apple Numbers: Autofill Repeating Formula?

Autofill will fill to the end of your table, it will not check for any results.

But you could set a filter for column D, then Number will only show rows where the result is >=0

Ralf

In general, B2-C2 is unlikely to come out to exactly zero. If B2-C2 comes out to less than zero do you want the result to be zero? Assuming that is what you want,

=MAX(B2-C2,0)

Another option is to carry down the remainder if B2-C2 would be less than zero.

=IF(B2−C2<0,B2,B2−C2)