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While the Apple 15" MacBook Pro (Late 2016) has four Thunderbolt 3 based USB Type-C connectors, it also allows the Plugable USB-C Triple Display 4K Docking Station with USB Power Delivery to be used to add on more connectivity by providing Ethernet, USB, DisplayPort, HDMI, and audio ports through a single USB Type-C cable to the Mac. Here we see how the Plugable dock supplements charging for the Mac which originally comes with the Apple 87W USB-C Power Adapter using USB Power Delivery quick battery charging standard.

The Apple 15" MacBook Pro (Late 2016) is powered on with the battery at 30% full when connected through one of its Thunderbolt 3 ports to the USB-C charging out port on the Plugable USB-C Triple Display 4K Docking Station. Looking at the GRL-USB-PD-A1 test analyzer application by Granite River Labs, after the first few Vendor Defined Messages, the Plugable dock starts to declare over USB Power Delivery to support 15 watts (5 volts @ 3 amps), 27 watts (9 volts @ 3 amps), 36 watts (12 volts @ 3 amps), 45 watts (15 volts @ 3 amps), and 60 watts (20 volts @ 3 amps).

We next observe the Mac initially requests to pull 3 amps @ 20 volts although here it shows that it can draw current of up to 4.4 amps. However with only max 60 watts (20 volts @ 3 amps) being offered, the Mac has to request this 60W power which the Plugable dock then accepts.

Later we also see the Mac rejecting Plugable's request to swap data roles, which is then followed by a continuous series of Vendor Defined Messages where we can also see DP Alt Mode being used between both devices. 

Once exchange of Vendor Defined Messages is over, the Apple 15" MacBook Pro (Late 2016) can be seen to again request the same 60 watts (20 volts @ 3 amps) as established earlier which the Plugable USB-C Triple Display 4K Docking Station also complies.  

When the Mac subsequently requests for Sink Capabilities, the Plugable dock indicates that it doesn't support any sink power with 0 amps @ 5 volts.

Over initial power requests and Vendor Defined Messages, the Apple 15" MacBook Pro (Late 2016) can be seen to start pulling current which frequently changes while at about 20 volts upon plugin at 30% battery and during power on. As the current increases to become more steady, the voltage lowers slightly for the Mac to eventually charge at around 59 watts (19.7 volts @ 3 amps).

With almost 60W, the Apple 15" MacBook Pro (Late 2016) is able to enjoy maximum charging that the Plugable USB-C Triple Display 4K Docking Station with USB Power Delivery can deliver. As comparison, the Apple 15" MacBook Pro (Late 2016) can charge faster with its own Apple 87W USB-C Power Adapter as seen previously.