Per the owners manual:
The boost gage is also equipped with three pairs of
lights that are located on each side of the gage. These
lights are used to indicate three different engine rpm
levels. The default setting for the lower pair of lights is
4,400 rpm, the middle pair of lights is 5,600 rpm, and the
top pair of lights is 6,200 rpm. These settings can be
adjusted by turning the stem behind each light. To have
the light pair come on at a higher rpm level, turn the stem
counterclockwise. To have the light pair come on at a
lower rpm level, turn the stem clockwise. Each turn
adjusts the settings by 100 rpm. To restore the default
settings, press and hold any stem for three seconds.
The lights will flash three times.
To turn the lights off or on, press and release any stem.
Hope this helps.