#ContSizeX is the width, in pixels, of the gump on top (the last one opened or clicked). It is the first half
of #ContSize as a plain number, so you can calculate with it without splitting the
x_y text.
Gumps on the ignore list (see IgnoreCont) are skipped.
Example
Section titled “Example”; click the bottom-right corner of the top gumpset %x #ContPosX + #ContSizeX - 10set %y #ContPosY + #ContSizeY - 10click %x %yhalt