When red LED is lit: Status 4 (COM)-3 contact during DRAIN (drainage) is conducted.
When green LED is on: During SUPPLY (water supply), contact No. 4 (COM)-2 is conducted.
If you understand it simply, you can understand it easily if you understand it as the LED position. If the red LED on the top is on, it is on the top, so the tank is filled with water.
If the green LED below is on, the LED location is below, meaning that the tank is out of water.
You just have to choose whether to use it as a water supply or as a drainage. Both LEDs never come on at the same time.
If both come in, it will be broken!