The Schedule % Complete specifies how much of the activity's baseline duration has been completed so far. Computed based on where the current data date falls between the activity's baseline start and finish dates.
The Schedule Percent Complete is used to compute planned value. Schedule Percent Complete, when displayed on an organized band and at the Project level, will ALWAYS be calculated as:
(BCWS * 100) / BAC
BCWS = Budgeted Cost Work Scheduled or Planned Value Cost
BAC = Budget At Completion
regardless of what earned value technique is selected for the activity's WBS.