GMC 2010 Yukon/Yukon XL Owner's Manual page 322

The radio supports:
Up to 50 folders.
Up to 8 folders in depth.
Up to 50 playlists.
Up to 255 files.
Playlists with an .m3u or .wpl extension.
Files with an .mp3, .wma, or .cda file extension.
The radio supports:
Up to 700 folders.
Up to 8 folders in depth.
Up to 65,535 files.
Folder and file names up to 64 bytes.
Files with an .mp3 or .wma file extension.
AAC files stored on an iPod.
FAT16
FAT32
4-100
The root directory is treated as a folder. Files are stored
in the root directory when the disc or storage device
does not contain folders. Files accessed from the root
directory of a CD display as F1 ROOT.
Folders that do not contain files are skipped, and the
player advances to the next folder that contains files.
Compressed audio files are accessed in the following
order:
Playlists (Px).
Files stored in the root directory.
Files stored in folders in the root directory.
Tracks are played in the following order:
Play begins from the first track in the first playlist
and continues sequentially through all tracks in
each playlist. When the last track of the last playlist
has played, play continues from the first track of
the first playlist.
Play begins from the first track in the first folder
and continues sequentially through all tracks in
each folder. When the last track of the last folder
has played, play continues from the first track of
the first folder.