ZSGG Academy of Orion Warfare
Like most RTS systems, ZeroSpace's unit/army capacity is based on supply. Each unit requires a particular amount of supply corresponding roughly to its power level. Unlike in some other games, in ZS your supply is used by army units only and not workers, so your current supply is a better representation of your army strength.
You have 15 maximum supply at the start of the game. Your hero will consume 10 of this supply. Each supply-producing building (Nourishing Pod, Idal Conduit, Supply Depot) will provide 15 additional supply. The Protectorate Supply Depot may also be upgraded for increased supply.