The square card was already filled with equally-sized squares, each containing a natural number.
This is a memory test method familiar to Qian Cangyi, with numbers from 1 to 49 arranged in a 7x7 grid.
However, the sequence of numbers is completely scrambled, meaning the top-left square is not 1, nor is the bottom-right square 49. There is no pattern to the numbers' arrangement.
The test method is simple: show the square card to Fan Yuantang for 20 seconds. In those 20 seconds, Fan Yuantang needs to remember the correct association between the squares and their numbers, and afterward, he must reproduce those numbers on an identical card but blank.
For the average person, a 7x7 grid is the limit; to go higher, one must either be a genius or have specialized training. And so, because of Fan Yuantang's earlier words, Qian Cangyi begins testing at 7x7.
