Mission Slots:

Your total available mission slots is based on your XP level.

The Mission slots can be divided between Earth Hunt/Harvest missions and Cocarro Siege missions. 

EXAMPLE: A Player at XP level 11 can occupy 10 Lands. On Earth, that means they can have 10 different Hunting/Harvesting missions active at one time. A player holding a Cocarro Portal Stone can divide those 10 missions between Hunting/Harvesting on Earth and Siege missions in Cocarro. However, they cannot exceed a total of 10 Lands occupied at one time.

NOTE: Explore missions, Quests, and PvP do not use Mission slots