Which port should I use to fast charge my laptop on the 200W USB-C 6-Port GaN Charger?

To charge a laptop as fast as possible on the 200W USB-C 6-Port PD GaN Charger (ST-C200GM-US), use the right port and cable.

How to fast charge your laptop on the 200W charger

Plug your laptop into the top port, labeled PD1. On the 200W charger, PD1 delivers the most power, up to 140W when it is the only device connected.
Use a USB-C cable rated for high power, since a thin or older cable can cap charging speed.
Understand shared power. This is a GaN charger, which uses gallium nitride to pack more power into a small size, and its ports use USB-C Power Delivery (PD), the fast-charging standard. The total 200W is shared across all six ports. When all six ports are in use, the split is about 65W, 45W, 20W, 20W, 20W, and 20W, so your laptop charges more slowly when other devices are connected.
For fastest laptop charging, keep the top port (PD1) for the laptop, and use the lower-power ports for phones and earbuds.