I was looking and nobody else had numbers on their arm. Very curious. Mark had also put that MOLE tattoo on his arm in Ep 2 and then he took it off later and made a remark about it in his confessional. So maybe he put the numbers on his arm himself just to mess with people. Just like Angie putting that little star on her face.

I also have MarkFOMO. But Dennis is suspicious. At this time I think Mark is the mole and Dennis knows it. Dennis told Mark that he had no reason to worry about being booted in the 3rd execution and yet he said he knew Stephen was going. If Dennis thinks Mark is the mole it would be a reason for him to tell Mark that Mark isn't going anywhere. But if Dennis knew that Stephen suspected someone other than Mark, he would assume Stephen could be going. I think Stephen thought Corbin was the mole and he was thrown off balance when Corbin was executed so he didn't know who to suspect in the 3rd quiz.