It is the first Time Interval ranging from Geometry rolled up till the final Geometry is stored as a Time offset value to be equal to the time value of the cumulative time of the video.
The cumulative value of Time Interval from the first to the Geometry Geometry is retained by the Time offset for the cumulative time at the time of the video.
A collecting value Time Interval since Geometry first, until the last Geometry were kept as the Time offset to the accumulated time equal to the time of the video.