Unseen Hours is the minimum time an area must not be seen by the player and deals with individual chunks (10 x 10 tile units of the map). This is to prevent zombies from spawning ontop of the player or in previously cleared areas.   Respawn hours deals with a much larger area (300 x 300 tiles) and Unseen Hours (chunk) is taken into affect when spawning zombies.   Some confusion comes from the redistribution mechanic. Many mistake zombies moving at a fixed rate from areas of higher population to