glad to hear the information here is useful, sometimes I never know.
The two LEDS are status indicators. The yellow LED shows if the device is connected to an app or not. The green LED shows when the device is active (making drops).
When the device is first powered on, the yellow LED blinks slowly. This indicates the device is on but not connected. After a connection to an app is made the LED stops blinking (turns on).
When the device receives drop data from an app, the yellow LED turns off, the green LED turns on and the drops are made. Once the drop sequence has finished the green LED turns off and the yellow LED turns back on.