[quote name='Puffa469']As other have said the 20gb hdd is only 13.xx GB. The rest of that space, over 6 gigs, is reserved for shit you can't delete, like the new look dashboard/blades and lame Avatar stuff.[/QUOTE]
I think that most of that 6 gigs is actually used for cache/swap space and for Xbox 1 backwards compatibility. The NXE itself only uses like 130mb and any avatar DLC you acquire probably just goes into your normal HDD space.