How is the Planned Time Variance Calculated in RTC Planning for Formal Process Template?

Hi All,

I am using RTC version 6.0.5, in the RTC Planning using Formal Process Template there is a view for Schedule Variance. I referred this link https://jazz.net/library/article/658 where it is stated that "the Planned Time Variance attribute indicates the difference in days between the current start date and the Planned start date for a given work item". Is the current start date used from the work item's actual start date or from accumulated dates in the Gantt chart view. Also does it consider the end dates for calculation of variance.

Thanks.