You don't have to pay too much attention to this matter. I've been paying attention to whether you practice calligraphy or not, and how it goes. So the teacher's small picture means that you can practice your handwriting with it. There must be a grid.
So go to the stationery store and look for it. It's a small notebook. The clerk will tell you that it is usually a 32K cube, or you can use 16K hard pen calligraphy paper, made in Mi Zige.