You're not missing anything, well not really.
Sometimes (but not all the time) when there are deleted posts, they are still included when the software that runs the forum determines how many pages there should be. But its as if they're all shoved to the end of the thread rather than being 'missing' where they were posted.
About the only thing that can be done to reduce it is to change the number of posts per page that are displayed in a thread. You can do it in your user CP, under options (
http://www.camaro5.com/forums/profile.php?do=editoptions). The default is 10 but you can set it to 20, 30, or 40 (I prefer 40). It won't prevent it from happening, but its the closest thing to a solution that I can think of.