I agree with you @jpfieber that the filter behavior can be a little bit fussy. When we built Autocat we thought the charge polarity may make the rules complicated (e.g. min and max amount ranges on expenses would both be negative) so we made the Min & Max filters work on absolute values. Most of the time, I believe this approach is helpful, but, in your case, it is confusing.
I think you will have more luck with the AutoCat “polarity” filter criteria. Just add a column to your AutoCat rules sheet called Amount Polarity then enter either Positive or Negative to the relevant filters.
Let me know if this solves the problem for you.
Randy
P.S. This functionality is documented here (if you search on “polarity filter criteria”) but it is certainly not well advertised or well known.