HLD-X9 has the same indicators on the front panel.
(from left to right: D-EXT / DIGITAL DATA OFF / CLOCK REF VIDEO / AUDIO [[ DISPLAY ]] DISPLAY OFF / SIDE A / SIDE B)
In the menu you can select if the Clock Ref should work for Video or Audio.
In another menu you can switch Digital data to off position.
And thats what these indicators tell.
Not related to MUSE, as these options are always available in the menu.
Tho to be honest, I never touched these options. Just never needed to.
EDIT: Meh, someone was faster
