duplicate SSID in scanning wifi result

i'm trying to make an app that can create a list of available wifi access point. here's part of the code i used:

x = new BroadcastReceiver()
        {
            @Override
            public void onReceive(Context c, Intent intent) 
            {
                results = wifi.getScanResults();
                size = results.size();
                if (results != null) {
                    for (int i=0; i<size; i++){
                        ScanResult scanresult = wifi.getScanResults().get(i);
                        String ssid = scanresult.SSID;
                        int rssi = scanresult.level;
                        String rssiString = String.valueOf(rssi);
                        textStatus.append(ssid + "," + rssiString);
                        textStatus.append("\n");
                    }
                    unregisterReceiver(x); //stops the continuous scan
                    textState.setText("Scanning complete!");
                } else {
                    unregisterReceiver(x); 
                    textState.setText("Nothing is found. Please make sure you are under any wifi coverage");
                }
            }
        };

both textStatus and textState is a TextView. i can get this to work but sometimes the result shows duplicate SSID but with different signal level, in a single scan. there might be 3-4 same SSIDs but with different signal level.

is it really different SSIDs and what differs them? can anyone explain?

Are you having several router modems for the same network? For example: A company has a big wireless network with multiple router modems installed in several places so every room has Wifi. If you do that scan you will get a lot of results with the same SSIDs but with different acces points, and thus different signal level.

EDIT: According to Walt's comment you can also have multiple results despite having only one access point if your modem is dual-band.