Today the matching used when creating a filter entry for the "level" field is by the word, alphabetic matching. So LessThan Critical would equal just Alert (A is less than C). This causes some confusion as one might think that Emergency, as the most severe/lowest numeric value would match, but it does not (E is not less than C).
Request is to have matching when comparing levels be based upon the well-defined severities in their severity level order - Emergency (0), Alert (1), Critical (2), Error (3), Warning (4), Notice (5), Info(6) and Debug (7). Making "LessThan Critical" include Emergency and Alert (going by numeric equivalent). Or maybe the other way around (going by more severe) - "GreaterThan Critical" is Emergency and Alert. Please make all operands work with this (EqualTo, NotEqualTo, GreaterThan, GreaterThanOrEqualTo, LessThan, LessThanOrEqualTo, Between) and document which - numeric or severity based - ordering is used.
TAC Case 372315 said this was a feature request, not a bug.