Not all users in author selection

I’m using version 2.9.1 with the following plugins:
– Role Manager 2.2.3
– Page Links To 2.1
– WP-PageNavi 2.50

When I’m at the page to add/edit a post, for some reason the only people in the authors list are the people in the group I created (posters), however I’m not (administrator).

I’m not overly concerned about this since author is not displayed on the site itself, however it’s useful for me to see who has done what.

Here is my site: https://nintendoaddict.com