Set Address on Map problem

I understand that the pin on the map in a listing cannot be set to an address outside of the default location unless one has the multilocation add-on. But how does the system figure out the borders of the default location? I am working on a directory for a small city in eastern Europe, single location, but I’m having problems setting up the address on a location on the “outskirts” of the town. What if the default location is a municipality?