metrojosie

So I was playing this mod because I like the idea of it. I noticed though that early on, maybe level 2 or 3 I went into a POI and started to clear it out and noticed zombies kept coming in from outside they just would not stop. I literally gained 3 levels in one POI from zombie kills. Is this the intended gameplay or was that a fluke? I didn't adjust the zombie count or anything and they were weren't "ninja spawning" in front of me, they just kept appearing inside from outside.