The busy hours, the Saturday, the delivery and the keys
Footfall in a shop is a curve with a flat top from eleven to four and a Saturday that is twice a weekday. A rota that puts the same three people on from open to close pays for the quiet first hour and the quiet last hour every day and is still short at lunchtime on Saturday. The rota that pays has an open and a close held by keyholders, a peak shift from eleven that leaves at four, and Saturday staff whose whole week is Saturday and Sunday.
Two more things shape a retail week. The delivery arrives before the doors, so someone is in the stockroom from half seven on delivery days and nowhere near the tills. And the keys: only two or three people can open and close, so every day starts and ends with one of them, and their holidays have to be planned around each other. A shop with a second branch adds a third: a supervisor who covers both, and the question of which branch is short this week.
Below is how a shop of twelve with two branches looks in InShift: the day across the branches on one screen, a person who covers the other branch, a rota handed out by invite code, and a manager who can see who is in at which branch from the phone.