EricPAI believe it just passes through whatever USB type-C power adapter is plugged into it but I'm not completely certain so you may want to do some research of your own.
EricPAI'd be interested in knowing this, too. I've got a little Satechi Slim Aluminum USB-C multi-port thing, and it steals about 10 watts from the pass-through to power itself. Or, at least, that's what my laptop reports when I start up with it plugged in. Plugging the charger in straight seems to deliver the full power.