Razer Huntsman Mini Analog

Hi, I have a question about my Razer Huntsman Mini Analog Fn button. When it's pressed the LEDs of the keys turn white to indicate which buttons have a function when Fn is pressed. All keys that don't have an Fn function stay dark. I'm a bit puzzled why the "compose" key (button right to the Fn button, box with three horizontal lines in it) light up when Fn is pressed, it doesn't seem to have a special function when Fn is pressed.