Hi James, thanks for you question. The 8 and 2 do become 10. But then we multiply that number by -1 (the number in the box on the upper left). The result is -10. The numbers in the second row, -1, 2, and -10, are what you get when you multiply each number in the bottom row (1, -2, and 10) by that -1 in the upper left box. The remainder, 10 + (-10) = 0, goes in the lower right box. A zero remainder tells us that -1 is indeed a zero of our polynomial.