Schedule tracking - SPI vs user perspective

Hi,

The scheduling tracking feature in Smartsheet shows that Parent Task is ahead of schedule for below, with Today = 10-Sep-2018

Task          From                 To                         Completion

Parent       06-Aug-2018     21-Sep-2018         83%

  Task A     06-Aug-2018    10-Aug-2018         100%

  Task B    13-Aug-2018     17-Aug-2018         100%

  Task C    20-Aug-2018     24-Aug-2018         100%

  Task D    27-Aug-2018     31-Aug-2018         100%

  Task E    03-Sep-2018     07-Sep-2018         100%

  Task F    17-Sep-2018     21-Sep-2018          0%

Completion percentage from Task A to Task F are input by user while Completion percentage of Parent is auto-calculated. And, Task F is scheduled in next week.

From my user's perspective, the project is ON SCHEDULE while the tracking of bar chart in gantt is AHEAD SCHEDULE.  See attached screen shot.

I think this is because the definition is different from each other.

In order to track the schedule from user's perspective, I have created the following two fields:

-  Expected completed percentage; and

-  SPI

with calculations below:

Expected completion Percentage

=IF([Planned Start]> TODAY(), 0, IF([Planned End] < TODAY(), 1, NETWORKDAYS([Planned Start], TODAY()) / NETWORKDAYS([Planned Start], [Planned End])))

SPI

=IF([Expected Completion (%)] <> 0, [Actual Completion (%)] / [Expected Completion (%)])

Eventually, the SPI calculated is exactly the same as what Smartsheet shows on gantt.

Question:

How to set the calculation if I want the result same as my user's expectation?

Thanks and regards

Frank