Access the User List (as administrator). All users are shown and sortable by clicking on column title (username, firstname, lastname. etc.). When the "description" column is selected only a sub-set of the users are listed.
The users shown when the "description" column is selected ... are those users that had the "description" field / attribute manually set / modified in the admin UI. This is true for those users that had an empty or existing value in the description field. Users that were created via an external system (LDAP / DB table), and had the description set, are not shown unless the description field is manually updated.