The Apple 29W USB-C Power Adapter was initially produced by Apple to deliver USB Power Delivery charging for Apple Macs but the charger can also be used with other non Apple products like the latest Samsung Galaxy Note 8 phone which also supports USB Power Delivery technology.
Over direct USB Type-C to Type-C connection, we observe the USB Power Delivery charging behavior of the Apple 29W USB-C Power Adapter and Samsung Galaxy Note 8 with low battery charge using the Granite River Labs GRL-USB-PD-A1 software. The Apple 29W USB-C Power Adapter starts communicating with the Samsung Galaxy Note 8 over USB Power Delivery by constantly showing that it supports 12 watts (5 volts @ 2.4 amps) and 29.6 watts (14.8 volts @ 2 amps) power profiles.
The Apple charger is then seen to initiate Vendor Defined Messages of Discover Identity and SVIDs with the Samsung phone.
As the Apple 29W USB-C Power Adapter starts charging the Samsung Galaxy Note 8 in the first 10 seconds, the phone is observed to briefly pull about 1.9 amps current at 4.8 volts upon first 12W power request. The phone then levels out charging at only around 5.9 watts (4.9 volts @ 1.2 amps) with the Apple charger after Vendor Defined Messages while the phone is active.
The Samsung Galaxy Note 8 does work with the Apple 29W USB-C Power Adapter over slow 6W charging despite the higher power that the phone should be getting from the originally shipped 15W Samsung charger through Samsung's proprietary Adaptive Fast Charging technology. The Apple charger can still act as alternative power supply just in case the phone desperately needs a recharge when the Samsung charger is not available.