Gain: A function that can increase the amplitude of the signal.
How to set: When you click Gain, a window like the one below will appear, and you can enter the desired value.

Gain: After entering the value, press the Enter key to apply it.
Fine Adjustment: If you want a fine adjustment of the Gain, click the triangle area to set it as precisely as 0.1dB.
CLR: Resets the entered value.
DEL: Deletes the entered value from the end.