Hi Sven.
According to the data sheet, all of them. There is a catch. And that is the total power of 55W. Depending on what you connect to the switch, this may or may not be enough.
For example, if a telephone needs 5 watts, you can connect 8 units. If you want to connect access points with 20W, it's over after 2 pcs.

I hope I have helped. The information is without guarantee.