Are you sure?
With "layered" I means a video file in witch EVERY frame is divided in 2 or more parts: a "base layer" (at lower bitrate) and one or more "enhanced layed" (for higher quality and bitrate).
Those files are usefull in streaming video applications with *variable* bitrate.
(But 99% of video files encoded with mpeg4 DON'T USE this special option)