Those are suggested space requirements. Chickens without enough space can develop some bad habits like feather picking and bullying. Your best bet it to watch and get to know your birds. Will you have predators? It's possible. Everything likes chicken. Make sure your coop and run are as secure as possible, and you can reduce your chances of predator loss. I wouldn't ever say a coop or run is 100% secure, because some predators can find the smallest opening and that's all they need.