That said, there is a way that you can see it, but it will show the users only for a group at a time and it will require a little 'work'. If you go to the Search for users section in your admin panel, select the group that you want to know how many members it has in the Primary user group selection field and hit the Search button. If the number shown is more than 20, which is the users default cut off pagination, you will see something along this line at the footer of the table: Showing 20 of xyz items. That will give you the precise members of said group.