When you stitch 9 2-1/2 together you should have a 2 inch center square because you sewed a 1/4 inch seam on all sides of it. The rest of the squares-all the surrounding 8 squares should measure 2 1/4 inches because you need to stitch them onto other squares. I believe the unfinished squares should measure 6 1/2 inches and the finished square would be 6 inches. In this case all squares would measure 2 inches finished. If you cut away parts of your 2 1/2 squares they will not match fit into adjoining squares in straight sets. Check to see if your 1/4 inch seam is consistent. It is easy to trail it off when you get to the far end of the seam.