Okay. So. For those who don't know (99,9% of mankind):
The Guiding Lands in Monster Hunter World iceborne are the final area unlocked in the Endgame. Most monsters from other areas appear in there with attack increased by some 20-25%. At the same time they drop special endgame items used to upgrade your gear.
For that reason the area is separated into sub-regions so that the monsters can spawn in their preferred biome. You won't see a ice loving Barioth spawn in the middle of a desert after all.
The higher the sub-region level the more monsters from that sub-region can spawn and the level tops at 7 when almost all monsters spawned are tempered - which means they're even stronger and drop special-special endgame items for upgrading...
But... There's a catch. You have a soft level cap of 27. Meaning that you can only keep 3 areas at lvl 7. At maximum you can have 7-7-7-4-1-1 in area levels.
The idea is that you're playing with friends and they have different areas at max lvl and you can play together to gather materials from all the monsters.
If you're playing alone you're doomed to look for randoms for help with that OR constantly re-level your areas to what you need at the moment.
Or... There's another option...
I've called it a "soft" level cap. That is because it slightly increases with each monster hunted in the area.
For each monster slain or captured you get 3*(lvl of region it spawned in) points so between 3 and 21 points. Those points are obviously hidden so you don't see them.
Those points increase your lvl cap.
You need ONLY 10000 points to increase the level cap BY ONE LEVEL.
Thus you need to hunt down some 7100 monsters to get all your sub-region to level 7...
I am not that crazy. I've just spent 4 months - hunting 10 (and later 15) monsters daily just to increase the cap by 3 and get a 4th region to lvl 7...
On the plus side - I got very proficient at fighting some of the game's monsters.