First is member status other than Adm or moderator is just that, a status that is awarded to the member for the number of posts on the board. According to the screen you pasted. You only have Cub Reporter, Meriwether,Kerth,Pulitzer. Because your setting for maximum number of messages for full membership is 50. Everyone should be a Cub reporter when they register until they make 50 posts. Then they are promoted to Meriwether. When they make 100 posts they become Kerth.
If a member is promoted from Cub Reporter to Meriwether with one post after you have changed your settings for promotions you may need to open a support ticket. Remember that existing member status levels will not be demoted. So the default was 31. You have changed it to 50. If a member was over 31 posts before you changed the setting they will appear as a Meriwether.