For the record, I'm only teasing about decreasing the counts. And I'm sure no one is evaluating your posts for "meaningful-ness"
Once in a while, a brand new member will try to get her/his post count elevated by replying "Me too" and "Nice post" to every thread on the board -- those people get a warning,
What you have noticed is that posts to the "Introduce Yourself" forum don't add to your count. And there are a couple others places, like the TEST forum, where your counter won't increase with every post.
But all your contributions to the "content areas" will auto-increment your count.