There are three classes that cover place:
Class 16/Pa- -- definite locations.
Class 17/ Ku- -- indefinite locations.
Class 18/M- -- inside locations.
Each of these has a form of "there is", pana, kuna and mna.
The reason mna can be both "there is (inside)" and "you (all) have" is because they are formed the exact same way -- with a noun class prefix and kuwa na. It's literally "this place has".
Pana = This precise place has. Prefix is pa-.
Kuna = Somewhere in this place has. Prefix is ku-.
Mna = Inside this place has. Prefix is m-.
The prefix for things that are inside happens to be the same as the second person plural prefix. The easiest way to tell them apart is context.