Checked with version: 2017.3
The Enemy Spawner prefab is located in the Project view, in Prefabs > Enemies. This controls the spawning of multiple enemies in your Scene at the location it is placed.
Prefab: The enemy Prefab to be spawned.
Initial Pool Count: This determines the amount of enemies which will be held in the pool. A good value to enter here is equal to the number of concurrent enemy that need to be spawned.
Total Enemies To Be Spawned: The number of enemies that the spawner can spawn until it stops spawning enemies.
Concurrent Enemies to be spawned: The number of enemies that the spawner spawns in the world at the same time. For example: If this is 5 with 10 total enemies, the spawner spawns 5 enemies. Once one is killed, the spawner spawns a new one, unless it has already spawned 10 in total.
Spawn Area: This is the extent of the spawn zone around the spawn point. Enemies are spawned at random positions within the zone. This can be visualized in the Scene view by the white rectangle gizmo around the spawn point.
Spawn Delay: The delay between the death of an enemy and the spawning of the next one.
Removal Delay: The time before an enemy is removed from the world and sent back to the pool.