When you install a smart device behind a wall switch, the position of the switch button is no longer important. As an example: before installing a smart device, the wall switch with the button position up meant the appliance, connected to it, was turned ON. After installing the smart device behind the wall switch, the button positions may be switched. 

This is because you can turn the device ON/OFF from the App on your smartphone/tablet and with the wall switch connected to the device. 

The logic of the smart device is programmed to check the change of the state of the connected device and not the position of the physical, wall switch.