What is confusing you is that the size would be what would
be showing when all the seams are sewn and the surface showing on the front side of the quilt would be 2 1/2 by 7 1/2
as the finished size. You would not have the 3 inch measurement once the seams are sewn together, hope this
clears it up for you. It would have the 3 inch before it is attached to the next block.