active pop count new round

[yeckoh]

The active pop count seems to be cleared on new-round by taking the current count and subtracting every existing zombie's cost. Why wouldn't it just get set to 0?
Eg:
Set the cost of immolators to 1 and spawn a bunch.
Reset the population cost back to 8.
With them still alive, end the round.
This goes both ways with having a negative or positive active pop count and 0 zombies depending on how much they cost at the time of spawning vs at the new round.