A single use license covers only one single edit. Each license includes one "sync," or edit, of the song that will be synced to a movie. If a cut down creates a new version or modification with a new sync, it is treated as a different project that requires its own license.
Lifts, on the other hand, are covered by a single license. When a piece of the video is "lifted out" of the project, it is referred to as a lift. This implies the project was not re-edited and the music was not re-synced in any way. Placement of the first 15 seconds of a video on social media is an example of a lift; the video is identical to the original in terms of sync and edit.