I need to extract the number of Unique Visitors using an app with each Operating System in a given Month. In other words, if user A uses the app with Operating System iOS 14.0 twice in the same month, I want the total for iOS 14.0 to increase ONLY by one.
In order to obtain this result:
I created a freeform table
I set the time interval to Jan 1, 2021 - Jan 31, 2021
I added Unique Visitors as the Metric
I added Operating Systems as the Dimesion
The problem is that the total for the Unique Visitors is 1,618,175 while adding up all of the rows related to the different Operating System I get 2,482,990.
I tried to replace the Operating System Dimesion with the Month Dimension: the total for the Unique Visitors remains 1,618,175 and the value for January is exactly the same.
My question is: why there is a 864,815 difference in Unique Visitors between the total for January and total for all the Operating Systems used in January?