This feature is available only in advanced_hls and fmp4_hls output formats.
You can now specify a media segment as a byte range (subrange) of a larger URL. This allows you to consolidate your media segments into larger files or a single large file. The primary benefit of this is when a client is playing your media, rather than downloading each successive segment file from a different location, it is actually walking through a larger file in sequence. Read more at Apple dev technote.
The Encoding.com API exposes this format of output by having the user request set the byte_range parameter to yes in a job request's stream section.