Well - any post that you make is counted, whether it's a first or a reply.
Second, it's entirely possible that during times of heavy loads on the boards they have it configured to not update the post counts right away. Take into account caching and other factors and times where you *think*it should have been updated , it wasn't and your browser is the culprit. You should be able to recreate this, I think.
Post something on one thread. Go the main part of the board and click the link for your post. Then click on 'New thread' and post another message (not a reply).
Then go back to the main board menu and reclick on the original message. Unless they are specifically resetting the timeout on the page, it may still show your original count.
In all honestly, it is an excercise in futility because they can and do archive old messages, and sometimes/sometimes not update the post counts. Ask Dan Murphy how many posts he *really* has made. Not what is shows....
