This is the specific function name, an instance of the fnDefName's definition, applied to this particular reference. Paired with fnDefName on the same row, this identifies exactly which named function instance governs this one reference within the network set, relevant when the same filter definition is reused with different parameters across multiple references. A value here distinct from another reference's fnName, despite sharing the same fnDefName, would indicate the two references apply the same type of filtering but with different specific settings.