I would like to calculate the average time spent session for an app. When I try to calculate it following this : Mobile Session Calculation I cannot find the same results as the ones that I find on Mobile Services.
Time frame : 1 week
On mobile services the average session lenght is : 20.68 minutes
When I calculate using the following data I don't get the same results :
Launches : 1656
First launches : 412
Total session lenght : 532373
Can someone clarify how we can get the same result as the mobile services one ?