flew SQ's a350 for the first time yesterday KUL-SIN

I quite like the IFE 'HUD' display (My flight) with the 'window seat' option that also shows a HUD like set of flight instruments.

There was one indicator which I could not make sense of

It looked something like

<--
nn |
V

ie two arrows (one left, one down) and a number (which varied from 15 through 23 throughout the flight, initially going up then down again)
I have not found any explanation of what this instruments is to represent.


I was a bit disappointed that when the plane banked the display did not indicate that but stayed level, and that it always showed as if at altitude (ie, before takeff and while landing the display of the scenery in the background was always from a highviewpoint).but the other instruments etc seemed to work fine. All that was missing was additional traffic (other planes) and maybe weather (storm cells etc) being indicated.