This is the third level of G7 compliance and the most stringent. G7 Colorspace includes all the requirements of the G7 Targeted level (and therefore the G7 Grayscale level) and adds the matching to an entire Reference Print Condition. This level demonstrates that you are maintaining extremely tight tolerances throughout the whole color space. An entire IT8.7/4 target is compared against the targeted color space and the average of all the 1617 patches needs to be with a narrow range of tolerances.
This assures that the printing system can consistently reproduce the entire color space and not just the primaries and secondaries (CMY and RGB). G7 Colorspace can also be relative to either the absolute white point or the substrate-relative aim values. G7 Colorspace level is also further divided into two separate purposes, Printing or Proofing. There are slightly more stringent requirements (tolerances) for proofing.