4 months ago - Shurenai - Direct link
The Blood Moon Count setting determines how many zombies are alive At One Time over the course of the blood moon night; as Seven said, this means when you kill one, a new on spawns at the edge of the loaded area to come pursue you.

How many spawn in Total is determined by your gamestage, which currently, is largely determined by player level. If at a given gamestage it would spawn 100 zombies, then 8 will spawn instantly, leaving 92 to go; You kill one, one respawns, 91 to go, and so on.

As Ragequit suggests, If you've raised your exp gain rate, That will result in your gamestage going up faster than normal- And so you'll hit higher tiers of gamestage, and by extension, larger spawning pools for the respawns to come from. At higher gamestages it's near impossible to exhaust the entire spawning pool @8 at a time so it becomes a siege until morning.