Should probably have told you why the batting needs to be 1/2" from the edge of the backing piece.... 1/4" of the edge will be taken up in the seam allowance, which will include batting from the quilt. Then when you flip the border pieces over, the seam allowance fills that additional 1/4" gap. It's a great smooth way to add borders with no lump, or "speed bump", as Marti calls it. She's a wonder. I highly recommend her Craftsy class on QAYG strategies.