Raid:
LFR - 17

Dungeon:
-- Seems to follow m+ key number 
M+2 = 2
M+3 = 3
...
m+8 = 8

Delve:
-- Seems to follow Delve Tier number
Tier 1/World Quest = 1
Tier 2 = 2
...
Tier 8 = 8
