I was teaching in a classroom modified from a dance studio. One of the walls was made of mirror, and the long tables students were sitting at were located straight next to this mirror wall. There were five young female students sitting at the tables in two rows. All of them had dark clothes and blond hair. On the other side of the class there sat another two students.
We started to form pairs for a learning assignment. I counted 7 students in the classroom, and said that we have to form two pairs and one group of three. The students said: “Why? We have even amount of us here!” I started to count the students again, and got the amount of 7, again.
Suddenly I noticed a young female student sitting next to the mirror in front of me. She also had blond hair but she had white shirt. For some reason I could not see her earlier. Although I looked straight at her, I was counting her as a mirror image.