This is a little counter-intuitive so I am quoting Ben Nadel here:
"ColdFusion applications do not really exist. At least not in the way you might think of a traditional desktop application that has a running process. ColdFusion applications do not have a constant process. Instead, they have memory scopes. Each application has its own name which ties it to a chunk of memory somewhere. Every time you define an application through the Application.cfc (or CFApplication), what you are really doing it associating the current page request to the chunk of memory that is associated with that application name.
When you start to look at ColdFusion applications this way, it becomes a little more clear why you cannot explicitly kill an application or a session; there simply is nothing to kill. An application doesn't run unless you have a running page that requests to be associated with it."
So how is a count of sessions calculated? Is it simply not gone until 8 hours (the default setting in the servers xml) has passed? Add it, wait 8 hours and subtract it?