From Mog to you: Darkhold full clear, 4 chests, 20 minutes remaining.

[Krausus]

a full clear is going in and killing your way to all the chests/bosses without skipping mobs
you really cant count the random mob down a hall that makes no sense cuz theres nothing in the hall lol

What makes no sense is killing mobs that dont need to be killed regardless of their placement, SE designed it to work that way.