Same thing happened to me. My guide on the plate is marked at 1/8 intervals. So I assumed what was marked as 2/8 was actually 1/4". Found out that it is actually 3/8 when I finally got around to measuring it earlier this week. I put a piece of masking tape there so I don't forget. Now I know why my Christmas wallhanging that I won't be finishing till next year...because of the problems of not have 1/4" seams...was a pain in the butt.