On the device menu of FaceStation 2, you can configure how far the device will scan a user. 

If you don't want the device to attempt to scan people that are passing by the hallway, you may want to set the motion sensor to a value that is lower. 

The visual camera scans the near object based on the change in the video feed and hence there isn't a exact angle or exact distance we can pin this value to, 

but an approximate value would be as follows:

Low : within 1.0m 

Medium : 1~1.5m 

High : 1.5m