OK. It has been my belief that it is the tiny bump that happens when pressing the seam to one side. But I don't press my seams open because that can cause another can of worms. I cut on the line just above the line thickness on the ruler and that solves the problem for me. If you are consistently just a tiny bit smaller, then don't worry, I would just piece the quilt as is. Does this quilt need to have a specific measurements? Then add the difference to the border. It is not going to be that great of a difference as long as your seams are ALL consistent.