Three answers
Each one takes the whole screen in its own colour, so a steward standing in a doorway knows what happened without reading a word.
Their name at a size you can read at arm's length, the ticket line, and anything they told you when they booked.
The time they arrived and which steward let them in, so nobody argues about it at the door.
Holds the screen instead of vanishing, because somebody has to deal with it, and offers to find them by name.
Several doors at once
A check-in is a single trip to the database that finds the ticket, changes its state and returns the count, all in one go. Two stewards scanning the same ticket at the same moment produce one check-in and one already in, and the second screen names who got there first.
Every scan brings back the running total, so the phone in your hand always shows where the room is up to.
On the phone
The count refreshes on this phone every time it scans, searches or checks somebody in.
When the QR will not do
A flat battery, a cracked screen, an email nobody can find. The roster opens over the camera from a button under your thumb. It starts by showing who is still to come, searches on name or email, and checks somebody in with one tap through exactly the same path a scan takes. There is a box for typing a ticket code by hand too.
Worth knowing before the night
Every scan asks the server. In a hall with no reception, check people in from the roster once you are back on data rather than at the door.
A steward needs an account on your workspace, and that account can see the rest of the portal. There is no door-only login yet.