fix wall error

Well. I have a stupid question for this fix wall command.
If I had a specific coord setting, such 290 in a 300-angstrom cube along the z axis, what is the meaning of the face setting lo or hi? There seems no need to have the zlo or zhi setting, just a z axis setting would be ok. But If I switch from zhi to zlo, there is the error again, particle on or inside the wall.
Or is my understanding of the coord setting right?

as mentioned before, it is very difficult to discuss this in such
hypothetical way. why don't you just provide a minimal (set of) input
example(s) of tiny system that illustrates your question? that would
make it infinitely easier to give specific answers.

please keep in mind, that LAMMPS will do *exactly* what the
documentation says (unless there is an error in the documentation).
however, you seem to be not following the documentation that closely
but rather prefer figuring things out empirically. that is not a
productive way.