That option needs a tool-tip, or some explanatory text, because many board houses do not yet support the "extended attributes". I don't know if it is selected, or un-selected, by default but I'd vote to leave it unselected.
In that same "PLOT" menu there are options for the numerical format (five decimal places versus 6), the option to redefine the origin using the auxiliary axis (this needs better explanation in the documentation!), and the option to include or exclude the outline ("Edge.Cuts") layer from all other plotted layers. Any of these options has a potential for getting your project files rejected by a board fabricator.