Does anybody know what number of controllers can this adapter join concurrently?

I discover divergent data on-line. I see 1, 4, 8 units… In the meanwhile I solely have 1 controller, so I can't check it, however this weekend I'll collect some pals in my home and I'd wish to know what number of units can I join into it.

https://preview.redd.it/1xvcexkbbhob1.jpg?width=800&format=pjpg&auto=webp&s=b722b665dbd450bada4f35e480c353a2ae87f0b1