The 2nd spot is for a Red TX lamp for radio's that don't have the small TX LED like your radio. The light there will only come on when transmitting. This turns the meter display red.I notice it has 2 spots for lights. Can you put 2 in it ?
You must use an drop resistor when using an LED.This is just 1 white led with no resistor. It was bright for about and hour then started going dim from there. I never tried to adjust the brightness till i noticed it going dim. I bet those 3 look awesome in yours. Im gonna get green to match the rest.