There is one line, and it's worth being precise about because it decides what your compliance record contains.
A unit's readings count toward a store from the moment the unit is assigned to that store. Before that — a unit that powered on and enrolled itself, or one sitting on a desk during testing — the readings are recorded and visible, but they belong to no store and appear in no report.
The practical consequence for a rollout: assign units promptly. A unit installed in June and assigned in August contributes nothing to that store's record for those two months, even though it was measuring the whole time.
In the dashboard: Dashboard — Every unit you're responsible for, with its current heat level. Switch between grid, stores, map and region views.