Cindy has a board that is 7 inches wide and 23\frac{1}{4}23 4 1 inches long. She needs to use the board to replace a shelf that is 15\frac{7}{8}15 8 7 inches long. Cindy hopes that the remaining piece of board is long enough to make a 7-inch by 7-inch square she can use to put under a house plant so it will receive more sunlight. How long is the remaining piece of board? (Give your answer in fraction form).