It depends on who gave Bree the list and why. Relevance means, "information which belongs to the topic". Say you and I were talking about this question, "hmm I wonder why Bree has this list??" - "I don't know Craig, I was hoping you might know?" - and someone else walks in to the room, and after listening to our conversation, says, "I like prawns but I don't like carrots!!!" - I'd say, "what relevance does that have to what we're talking about?". So, "relevant numbers" would be numbers which had a reason to be noted - for another purpose. (I'd actually, in real life, say something which would get me banned from italki haha but that's another thing all together!)

My guess is that meant "the numbers that matter" or "important numbers".

It basically means "numbers of importance", "useful numbers" or "numbers that are relevant". Relevance = the degree to which something is related or useful to what is happening or being talked about; closely connected or appropriate to the matter in hand

"Numbers of Relevance" I think in this case means numbers that are relevant to something or someone. In other words, they are important or somehow have some importance to a particular subject or matter. So, in the short scene that you describe the numbers on the list are relevant in that they are the codes to open particular lockers in the locker room.

All answers are perfect. It was so hard to pick one. Thanks all!