When your device has no GPS signal it will show a gray circle to indicate this. The gray circle is not the size of the radius that you have set for this location, just an indication that it does not have GPS signal at this time.
GPS technology has limitations, regardless of AngelSense, that we essentially try to make the best of using our analytics. GPS reception indoors is poor due to not having line of sight with satellites, along with GPS limitations in general. Once the device is able to gain GPS signal upon leaving the indoor location it will resume sending the GPS location.