To join a match, open it and tap "Opt In." If there is room on the roster (fewer confirmed players than the max), you are immediately confirmed. If the roster is full, you are added to the reserve queue.
To leave a match, tap "Opt Out." Your spot is released. If you were confirmed and there are reserves waiting, the first reserve is promoted to fill your spot.
Each match has a maximum player limit set by the group owner. Once the confirmed roster reaches this limit, all additional opt-ins are placed in the reserve queue. The group owner or admins can adjust the max players at any time.
The reserve queue is ordered first come, first served. When a confirmed player opts out or is removed, the reserve at the front of the queue is next in line for promotion. How promotion happens depends on the group's slot offer mode (see Slot Offers).
Group owners and admins have additional roster controls: