When set, the item will be started earlier so that it arrives at Preroll by the time the previous item reaches its mix point (Start Next or Fade Out).
Example: Cue In at 0:01, Preroll at 0:06 - item will begin to play 5 seconds early.
You should be able to observe the effect in the Mix editor.
Important: It only works in containers at the moment. Will be ignored when the item is played individually.