There are two more memory registers that are used for plotting. If the minimum x value for a plot is put in Memory 0, and the maximum x value is put in Memory 9, then the plot will show the y axis at x = 0 (if x = 0 is on the graph). The point coordinates will also be shown in (x,y) form rather than in (pt.No, y) form.
These memorys may also be used for general storage if not needed for plotting. The values in memorys 0 and 9 are transferred into the appropriate fields in the plot stack, so be sure that meaningful values (or blanks) are therein if you do go to the plot stack.
The plot registers can be displayed by holding down the command key while clicking in the small round "Show memory" button. The appear at the bottom of the screen (min on left, max on right). Click in either one of them to hide them again.