OPTION EXPLICIT
causes VB to post an error message ("variable not defined") if you try to use a variable that has not been Dim'd (maybe because of a misspelling). Also, if you try to assign data to variable which does not match the TYPE in the Dim statement you will get an error ("type mismatch"). For instance if you define, say TOTALCOUNT as Long, then somewhere in your code you say: TOTALCOUNT= "testing 123" (a string) you will get that error.
OPTION EXPLICIT makes troubleshooting code much easier and you should insist on using it always.