This week we know that a man goes to exile island. We see his forearm. Study it... figure out who it is, and maybe based on that knowledge you can gain insight on which team wins... and choose accordingly
I saw that preview and I'm not 100% sure this is accurate. I think that may have been a Survivor staff member's arm they were just showing to make things look exciting, sort of like how they get random people to go through each challenge before it starts and show you how it works.