"You're on the list" isn't about YOU physically being on the list, it's your name which is physically on the list. Prepositions sometimes don't make very much sense and (although nobody likes to hear this) are really something you just need to memorize. I had the same trouble in Russian when learning how to properly use в & на

He's the first on the list. <--- To be the nth item on a list typically means that thing appears as the list's nth item. So that is the default interpretation. However, you could construct a small dialogue in which this wasn't the case. For instance, "Mark: Every morning, Tammy and Spenser step onto my list that I leave out on the kitchen floor. -- Dan: Who's the first (one) on the list? -- Mark: Spenser is the first (one) on the list." This is kind of a pun in a way. I think people would roll their eyes at this though because who ever stands on a piece of paper with a list on it? Hahaha. :D Actually, you could make a pun out of this sentence: Mark: Are you on the list? -- Dan: Yes. -- Mark: Then get off of it. You're going to leave footprints on it. -- Dan: Omg. You're an idiot. He's standing on the list. <--- This one definitely means physical location. Why? Because I used the verb "to stand" along with it.