The HorizBody and VertBody variables describe the standard increment by which the pot variables change and the relative size of the knob when auto-knob is used. The increment, or typical step value, is the value added to or subtracted from the internal knob position when the user clicks in the container around the knob. For example, a proportional gadget for color mixing might allow the user to add or subtract 1/16 of the full value each time, thus the body variable should be set to MAXBODY / 16. Body variables are also used in conjunction with the auto-knob (described above) to display for the user how much of the total quantity of data is displayed. Additionally, the user can tell at a glance that clicking in the container around the knob will advance the position by an amount proportional to the size of the knob. For instance, if the data is a fifteen line text file, and five lines are visible in the display, then the body variable should be set to one third of MAXBODY. In this case, the auto-knob will fill one third of the container, and clicking in the container ahead of the knob will advance the position in the file by one third. For a slider, the body variables are usually set such that the full percentage increment is represented. This is not always so for a scroller. With a scroller, some overlap is often desired between successive steps. For example, when paging through a text editor, one or two lines are often left on screen from the previous page, making the transition easier on the user. The two body variables may be set to the same or different increments. When the user clicks in the container, the pot variables are adjusted by an amount derived from the body variables.