Centering concentric circles...fancy way to say the centered shoe fits in contact with more of the drum when applied. With the brake applied (pressure on the brake) loosen the anchor bolt and the shoes match the drum. With pressure still applied retighten and...you get better brakes. Drum only tech tip. And most don't know about it. Critical when working old marginal brakes like motorcycles. And...worse if you have antique mechanical brakes. Before self adjusting, and proportional valves, and 70 MPH roads with a load. We keep trying to make these old trucks work in a modern world. They can use all the help we can give them.
