Solution when you get an erro: Return code of -1 is out of bounds

It works well.
I set wrong parameter value with this script and I found an error that its message was “Return code of -1 is out of bounds” from Nagios Web UI.
It was not intended thing. It was because wrong exit_code in the code:
%exit_codes = (‘UNKNOWN’ ,-1,
‘OK’ , 0,
‘WARNING’ , 1,
‘CRITICAL’, 2,
);

If you change of ‘UNKNOWN’ to 3, you would not be given that message, instead, you get proper error massage like this:
“*** WARN level must not be less than CRITICAL when checking FREE memory!”