Haha!She's starting to think the rumbling sound might be because she hates being underground and the blood is roaring in her ears.
"Finally, proper stonework." grumbles Kilian. Clearly he's appreciative of both the stonework and being underground both.
You are correct. They are heading to 5. The party will slowly head west toward the middle of the hallway (but staying on one side). Once they get near the second northern passage, they'll likely detour to see what the two 2's on the map are. That symbol occurs elsewhere.
Any signs of spiders or other creepy crawlies? How high is the ceiling, and can the party see the top of it?
I don't like the alcoves in this hallway.