The 2017 manual says the Energy Details screen displays how energy is being used since the last time the high voltage battery was fully charged. If the above interpretation is accurate (you’ve used 85% for driving/accessories, 0% for climate settings and 0% for battery conditioning, and 15% remains to be used), then if you partially recharge your Volt right now and unplug before fully recharged, the 85% should drop to reflect that the 12.1 kWh you’ve already used is now a smaller % of the total grid power pumped into the battery since the last time the battery was fully charged.