The bobbin in the picture isn't a Bernina bobbin -- it has 10 holes. It's a cheap Singer bobbin. A Bernina bobbin has 7 holes, and a tighter center shaft hole. See the little hole in the top of the machine? If you turn the screw a little one direction or the other, it will adjust the even-ness of the bobbin winding. Start with a good Bernina bobbin before you start adjusting the adjustment screw.