We have post counts there to highlight who are more frequent members here, but it can be inaccurate and unfair to those who are newer to those who are older. The best method to use, which I often look at when updating ranks, is the "per day" count on the profile page... which ignores how long you have been here, just how much you interact here.
I do have records of when members first joined Ozformers for most of the members before we moved here, so I'd like to have the "original" join date next to the "current board's" join date... but as I noted above, this doesn't appear obviously easy to do (for me).