@gnz 

For mesh routers, client devices like smartphones usually detect only one SSID. In your case, it appears that the app has separately scanned both SSIDs of the mesh units. You can choose either SSID to continue the configuration. If that fails, try selecting the other SSID during reconfiguration.

From my experience, as long as the phone's location hasn't changed, the order of the WiFi list should stay the same.