A display apparatus includes a first display plate, a first electrode and a second electrode disposed on the first display plate, a second display plate, a third electrode disposed on the second display plate, and a liquid crystal layer disposed between the first display plate and the second display plate. Where the edges of two servo bursts are used to define a position on the media, trimming the first burst and writing the second burst on separate revolutions of the media will result in a different amount of position error being written into each burst. After the water removal of the former part of the dialysis operation, when the circulating blood volume in the body attains the standard blood volume, the latter part of the dialysis operation is started.