The reference plate position was adjusted;

- previously: the side facing us (where the plane mirrors are located), the distance between plane mirrors was smaller than spherical. 

- now: its position was reversed, the distance between the plane is grater than spherical.

***A good way to always notice this immediately is the marker (pointed in the red circle) at the top left in the picture attached.

The plate should always be placed in a way that the marker should be located on the spherical mirrors side on the left away from us.