Bind plus and minus signs to operators

Hey guys, Unfortunately, it seems to be not possible. Originally '-' and '+' are bound to motions and that certainly works. However, if one tries to bind them to some operators, then `evil-extract-count' throws Key sequence contains no complete binding It's a bit difficult for me to understand the exact reason for that. Probably this has something to do with misinterpretation of prefix numeric arguments. Is it possible to fix that? If not, could you elaborate on why that would be not possible. Thanks and regards, Alexander