Once you sewed the 6 in. squares, each one was 5 3/4. In the second picture, I think that you can see that the top piece that you cut off is a bit wider than the other part of the top of the square. That is because the part that you cut off will be sewn to the bottom 2 squares. So, you cut the top 2 squares by leaving 2 3/4 attached to the bottom 2 squares; the cut off piece should be 3 inches, which will end up by being 2 3/4 inches after it is sewn to the bottom two squares. The same math will apply to the side piece that you cut off in the second row of pictures; you leave 2 3/4 inches with the main block and have a 3 inch piece left to sew to the other side of the block.