They charged it at the default 8A at 120V. That default was chosen to avoid issues with marginal 120V outlets or circuits with other devices plugged in. If you have a socket in good condition and a dedicated circuit then you can change the charge current to 12A and the Volt will remember that setting based on its GPS location so you don't have to keep overriding the 8A default like you had to do in some earlier model years.
Good to know. Man, I should start keeping a table of the different vehicles, charging capability and so forth. It varies so much from vehicle to vehicle.