I think what she is saying is that after sewing her seam, there is a small amount of fabric that has been pushed past the end of her stitching line. I have noticed that when using a less expensive fabric specially on the top of pieces being sewn, that the pressure feet push the top fabric piece, in essence stretching it past your bottom fabric. This has happened to me more times than I wish to count, until I figured out what was happening. Now I lay my two pieces of fabric together, spray starch & press them TOGETHER, then pin at both beginning & ending of that seam I'm going to sew. When I use higher quality fabric I do not have this problem. It happens more so if you are sewing cut triangles because your sewing the bias, and it really stretches.