In the first instance, you will note that everything seems normal, everything is balanced. Things are where they belong.

In the second instance, however, in my reading, the "boy" exists in the real world, the readers have moved into the box in front of Erised, and Potter has moved out of "story" box. In addition, the fantasy and the allusions to our world have changed color.

In the last instance, the fantasy has taken over. Potter "exists" in our world, in our box, the boxes have fallen completely under the sway of their individual Eriseds, and the "boy" has been pushed almost out of the picture.