Seems like this chart could work both ways---- Teacher could be in charge of it as she sees fit. Also, student could move his/her name pin to whichever category he's feeling. That could clue teacher into the internal dialogue of a particular student.
I see it could be two ways. One: the big dog is very kind and left the big bed for the pup. Two: the pup went on the big bed and left the small bed for the big dog. In that case, if I was the big dog, I would just lay on the small dog (or around it).