Folks with a reservation for a group study room lose the ability to reclaim it 15 minutes after the start of their reservation. Please be understanding if they have just zipped out to the restroom or to collect a book.
On the other hand, they can't go off to lunch and expect the room to wait.
If you run into issues, please let the folks at one of the second floor service desks know and they will contact the building monitors.
It takes a minimum of two people to be a group.