Ok, now I understand
These 2 screen captures, nothing changed, the tank didnt move, the turret nor the cupola moved, but the angles are different.
In the first image is taken from inside the tank, the view is out the "window", and the windows is at 15 which means its 90 degrees from the front of the tank. Remember the 180 degree range from directly forward to directly backwards is represented by 30.
In the second image from the outside, the number represents the angle the camera is looking, since the camera is looking from directly behind the number reads 0.Notice from outside the periscope is oriented 90 degrees from the longitudinal axis of the tank.User must be aware of the which crew member, which sight, and which viewpoint are selected to make sense of this interface.