@AndrewOlsson This is working as desgined behavior.
I understood the scenario, when "All visits" segment is used it gives different Avg time on site while it gives different value compared with the "Month" dimension
Below is the explaination for you.
Below is the explanation on the same
For example, for the month of July, if we had two visits in the same month, so the sequence will be 1.
July 3
Visit 1
Hit 1 - 10
Hit 2 - 20
Hit 3 - 10
Total seconds spent - 40
July 5
Visit 2
Hit 1 - 20
Hit 2 - 30
Total seconds spent - 50
Aug 3
Visit 3
Hit 1 - 10
Hit 2 - 20
Hit 3 - 30
Hit 4 - 40
Total seconds spent - 100
July-August report
All Visits segment :
Average Time on site: (100 + 50 + 40)/3 = 190/3 = 63.3seconds
However the normal free form table with Month as the dimension
July = (50+40)/1 = 90 seconds (as it's essentially the same month so the denominator sequence will be 1)
August = 100/1 = 100 seconds
Hope this explains