Question on stealth checks in fortress - Adventure One, Chapter Two

[Tobold]

On page 120 of "The Investigation Begins" / page 28 of "The Island at the Axis of the World" there is a text box about Fortress Security. It says that moving between areas requires stealth checks, with the number of failed stealth checks determining the alert level later when holding the lighthouse. I'm not quite clear about how exactly to handle those:

1. What is one "area"? For example if the group moves from the passwall along the wall to the right until the lighthouse, how many stealth checks does that require? Does that correspond to "explore outer fort" requiring just 1 check of DC 8?
2. Are these group stealth checks or individual stealth checks? So if I require a stealth check from everybody and 4 players fail, does that count as 1 failed group check (mild alert) or 4 failed checks (elevated alert)?

 

[The1exile]

When I ran it, I had moving around the outer area up to the gate on the map between the outer fort and the docks (not to the lighthouse itself) be one round of checks. After that I improvised something for them trying to bluff their way through the gate. Each character's failure counted as one failure, because I only used the guard alertness mechanic to limit them going everywhere in the fortress before their reinforcements arrived, and if I did one failure per party check then they would have had loads of attempts.

For this particular section I would recommend you just remind the players of their mission (i.e. to open the sea gate, not to scout the entire fortress) and improvise any challenges rather than relying on the book's explicit rule.