Server-side While do counter detects ChildAdded but ignores ChildRemoved?

I made an NPC spawner script that puts a cap on how many zombies can spawn, but I can't figure out how to tell it to spawn more when the cap decreases/a player kills one, it seems to ignore ChildRemoved and stop spawning them even after I cut them from the spawner in Run mode.

local child = game.workspace.Spawn.ChildAdded:Connect(function(child)
end)
local abortion = game.workspace.Spawn.ChildRemoved:Connect(function(abortion)
	
end)

local ZombieCount = 0
local NPC = game.ReplicatedStorage.Zombie
local spawner = game.workspace.Spawn
while ZombieCount <5 do
local Clone = NPC:Clone()
	Clone.Parent = spawner
	Clone.Torso.CFrame = spawner.CFrame
	wait(1)
	if child then ZombieCount = ZombieCount +1
	elseif abortion then ZombieCount = ZombieCount  -1
	end
	end

Is there a better method than ChildRemoved or am I just using it wrong?

Is the counter even supposed to be in the while do loop?