How are you viewing the total number of active users that would allow you not to be one of them? Does that make sense? If you are viewing a page on the server, and therefore have started a session with the server, then of course there will be at least one user active.
Just another note on your code as well, if your goal of the Application_OnEnd() is to gather the total number of users that have visited your site between application runs, then it will not work. Since you increment and decrement Application("visitors") everytime a session starts or ends, then when the application ends, you will only get the total number of active users at the time the application was terminated. You should increment totusers every time a session starts and leave it at that, otherwise your numbers won't be accurate.