The 100w are for the sum of all ports, but only the first port can output the full 100W. I now use it instead of the 140W power supply on my MBP and am very satisfied so far. There are a few videos about the device on YT.

On the manufacturer's website there is a picture of the different possibilities of how much power the USB ports can deliver in which combination. https://u-green.ch/products...

For one port 100W PD - there are different configurations and it depends on the port. But it is the best on the market today.