The reflection image they use is not physically possible.
Look at the angle of the view in relation to the 'register monitor', the blue counter area, and the lady customer.
To produce the angle of register monitor in relation to the blue counter area, the shot would have to come from the left of the cashier, shooting across to the right (to get the blue counter area to the right of the register monitor).
To produce the angle of lady customer in relation to the register monitor, the shot would have to come from the right of the cashier, shooting across to the left (to get the register monitor to appear in 'front' of the lady customer). Note: and the lady customer would be facing the opposite direction.
So where do they suggest you place the camera/mirror, and what is it supposed to actually be watching/recording?