getting users on my radius via geofire to a list and rules

Question

so to this points im facing 2 problems, first one is

Using an unspecified index. Consider adding '".indexOn": "g"' at Geofire to your security and Firebase Database rules for better performance

while running the app those are my securety rules via firebase

{
  "rules": {
    ".read": "auth != null",
    ".write": "auth != null"
  }
}

this is my database

second question, im trying to get the number of users on my radius except me, for some reason , im finding only one eventhough on the database theres are 2 at the location , and radius is 100km, here example of the code, please help me

final Set<String> runnersNearby = new HashSet<String>();

geoFire.setLocation(uid, new GeoLocation(lat, lang));

GeoQuery geoQuery = geoFire.queryAtLocation(new GeoLocation(lat, lang), radius);
geoQuery.addGeoQueryEventListener(new GeoQueryEventListener() {
    @Override
    public void onKeyEntered(String key, GeoLocation location) {
        Toast.makeText(UserProfile.this, "Successfully Found", Toast.LENGTH_SHORT).show();
        if (key != user.getUid())
            runnersNearby.add(key);
        Log.d("Number of users", String.valueOf(runnersNearby.size()));
        Log.d("KEY", String.valueOf(key));
    }

    @Override
    public void onKeyExited(String key) {
        Toast.makeText(UserProfile.this, "left the place", Toast.LENGTH_SHORT).show();
        runnersNearby.remove(key);
    }

    @Override
    public void onKeyMoved(String key, GeoLocation location) {
        Toast.makeText(UserProfile.this, "key moved but here", Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onGeoQueryReady() {
        System.out.println("All initial data has been loaded and events have been fired!");
    }

    @Override
    public void onGeoQueryError(DatabaseError error) {
        Toast.makeText(UserProfile.this, "Error Occured", Toast.LENGTH_SHORT).show();
    }
});

Answer 1

The message is pretty explicit:

{
  "rules": {
    ".read": "auth != null",
    ".write": "auth != null",
    "Geofire": {
      ".indexOn": "g"
    }
  }
}