The Reports page gives admins a snapshot on how their seats have been allocated.

Purchased – The number of seats that a group has paid for or has access to.
Assigned – The number of active users and the number of pending invited users.
Available – The number of available seats that you must invite new users or to reactivate old users. 

*If an admin runs out of seats and would like to add users to the group license, they can contact for a prorated license quote. After we have received payment or the purchase order for the quote, we will add the seats to the group license and notify the admin.