The list for di is {-1 ; -1 ; 2 ; -3 ; 4 ; -5 ; 1 ; 4}
You got this list by substracting the values for yi from the values for xi : di = xi - yi
So, for example, d1 = x1 - y1 = 5 - 6 = -1

Now, form the square of the difference between d1 and d-bar (average value of di), and add them all :

(d1 - 0.125)² + (d2 - 0.125)² + ... (d8 - 0.125)² = 72.875

The next part is surprising, I would rather divide this sum by n (namely : n=8) to find the variance of the differences.