Structure Formula: Convert timeSpent number to weeks

[KD]

I am working with a Formula column on my Structure board. In this Formula, I want to convert timeSpent into a number value, in weeks. Ultimately, the purpose is to then divide that value by another number that is already in weeks, then display the final Formula column as a Percentage.

I am struggling to get timeSpent converted to weeks correctly within my Formula.

• When I make a separate "Σ Time Spent" column, to compare it as a control, it shows: 11w 2d 7h 40m. ~11 weeks is the correct number, which I am trying to get to within my Formula.
• In my Formula, timeSpent displayed as a Number, shows: 1669200000
• To confirm there is nothing wrong with my Formula, I can change the display to Duration, if I check "Work Time" ON then the Formula displays correctly: 11w 2d 7h 40m. 
• If I check "Work Time" OFF, then the Formula displays 2w 5d 7h 40m, and I have no idea how this value is being calculated... :(

Using Google time converter, 1669200000 milliseconds does not convert  ~11 weeks.
However.. 1669200000 milliseconds does convert to ~2.7 weeks...

Any ideas on what formula Structure is using to get 1669200000 into ~11 weeks, similar to Duration "Work Time" ON, so that I can replicate it within my Formula column??  

Here are some screenshots demonstrating...

[KD · Accepted solution]

I think I was able to convert my total milliseconds into workweeks by dividing it by the number of milliseconds in 40 hours. :) 

[KD]

[KD]

It seems like the ~2.7 number is total time, whereas "Work Time" uses your Jira work settings. So I need a formula to convert total time into Jira weeks. (My settings are 5 days in a week, 8 hours in a day.)