https://experienceleaguecommunities.adobe.com/t5/adobe-analytics-questions/get-only-the-marketing-ch...
You are in luck, I asked a similar question last week and got a good answer. There is the link. I will recap.
Deduping will occur with visits because visits is not a 'standard' metric. It is the container for all activity for unique visitors.
So depending on what dimension you are using, you will see that some of them have multiple occurences per visit.
If you want to see a distinct count, one of the ways to get that number is to be more specific than visits.
For instance, you can use the exit page, or entries page metric. Also not standard, but more specific as they are indicating a single 'thing' and not a 'bucket of things'.
The deduping you see in the grand total numbers are done on adobe's side. You can't see how the dedupe is actually done.
If you can be more specific about which dimensions you are using, and by what you are breaking them down, I can also be more specific.
But that is the gist of it.
