You can set your own rank names for your Forums depending on number of posts.
Moderators, Administrators and Super Administrators have set ranks which are not affected by post count.
Forum Ranks must be enabled in Administration -> Settings -> Forum Settings -> Enable forum ranks
Rank Title: Enter the rank name
Rank Image: Select the image to correspond with the rank
Rank Posts Set the number of posts required for the rank to be achieved
Apply to: Select the user level this rank applies to.
This shows all the ranks and their respective levels you have chosen, to alter just click Edit.