The [Gamut Data View] maps a rough wire frame representation of the gamuts on an L*a*b* axis. This allows you to visually determine if the proofing gamut fully encompasses the final output gamut. If the proofing gamut does not completely encompass the final output gamut, it cannot accurately reproduce the color of the final output printer.
You can adjust your view of the gamuts displayed by moving the sliders. Each slider controls one axis of the L*a*b* axes.