Need help with player counter

I need help to make a player counter. I want to split the players into 1 versus all. Ive looked at guides but no help. Anyone know the solution? (I want the max to be 1V9)

zone and a counter
zone the size of the map

Now that I just saw it, the images for the guide were down again
First do what @How_Was_The_Fall said, and I assume you want it to be live, then
Player enters zone-increment counter
Counter linked to a property
Counter decrement when player knocked out
Also make a game overlay or whatever tracking the property
This system can’t account for player leaving but it’s pretty easy to make