@ Inf Allycat - The post count show the total of all posts made. The profile only shows the most recent of the last 200 threads that a person has posted on.
When a thread reaches the end of page 50 of a forum, it 'falls off' and is no longer available. If the poster has posts on threads that have since fallen off the forums, those posts will still be included in the post count, but will not appear on their profile, as they no longer exist on the forum.
Similarly, if a user has access to a private forum, such as the Clan Leaders Forum, High Level Forums, or the Gold Premier Club forum, the post count will include posts in those forums, but those threads will not show on their profile unless the person looking at the profile also has access to those forums.