Not sure if Gen 2 is similar, but on Gen 1 if the "relearn" procedure was not performed to exacting standards, the Volt has to "relearn" on its own the correct SOC for charging and depletion. In the meantime, it will default to "safe" values that are way more conservative than normal. This takes several (perhaps 10--WOP knows the full amount) complete charges and discharges before it will start getting back to normal.
My advice is to make sure you deplete the battery fully after a full recharge and avoid partial charges for at least a couple weeks. If it doesn't start creeping up to normal, time to take it back.
Also, I think another Gen 2 owner had a similar issue after the recall, so you may want to look for that.
***2013 Black Volt, Leather with Ceramic White Accents***
***17" Sport Wheels, Nav, Bose, SP1***