I showed it once to a professor of physics, and his first reaction was wow, but then he thought about if for about 3 seconds and explained to me how it works. Note that the result that you get always divides by 9, and that all the numbers in the table you get in the end that divide by nine have the same symbol. The symbols are changing, but it's always the same symbol for all the numbers that divide by 9 and the symbol that appears in the end.