Remember that the vector between two points, A and B, can be defined two ways: from A to B and from B to A. For this reason, the bins in the 1st and 3rd quadrants are identical, and so are the bins in the 2nd and 4th quadrants. This is why the semivariogram map is symmetrical about the two diagonals.
Keeping this in mind, you need to pick two quadrants to use (we use the 1st and 2nd), then you'll need to inflect any weights that fall into the 3rd and 4th quadrants. Be careful not to double-count each pair.