2 Modules combined

2 Modules combined

Hello,

We have 2 modules : 
1. Visit Reports 
2. Hits

I would like to make charts and widgets to see how many visits are done per hit and this ideally per user over the months.

How can I do this because when I create "add aggregate formula" in the table it says it's not possible (see attachment).
I don't know how to do this, could someone help me doing it in live session ?

Thanks