Different indicators let you see at a glance if everything is fine : the status, the FPS, the camera feed (it should not be black) and the OTS status (the OTS need some time upon start to initialize, during this initialization phase, the OTS status is set to Ok, noisy). The aim is to get green check marks across the board.
In order to have a correct tracking, you need to have at least 8 FPS (Frames per Second) : a lower FPS would prevent a good tracking, resulting in a risk to count people twice. To increase the FPS, you can lower the camera resolution – do not rush to the camera parameters immediately though, the software takes some time to reach cruising speed.
If you have under 8 FPS, you will see a warning red mark: 
These colored marks apply to each field, with the same meaning:
green for good,
yellow for okay,
red for warning