Update User Cap documentation

doc/user/admin_area/settings/sign_up_restrictions.md

@@ -51,10 +51,13 @@ To enforce confirmation of the email address used for new sign ups:
 
 > [Introduced](https://gitlab.com/groups/gitlab-org/-/epics/4315) in GitLab 13.6.
 
-When the number of users reaches the user cap, any user who is added or requests access must be
+When the number of billable users reaches the user cap, any user who is added or requests access must be
 [approved](../approving_users.md#approving-a-user) by an administrator before they can start using
 their account.
 
+If an administrator increases or removes the user cap, the users in pending approval state will be
+automatically approved in a background job.
+
 ## Soft email confirmation
 
 > - [Introduced](https://gitlab.com/gitlab-org/gitlab-foss/-/issues/47003) in GitLab 12.2.