That's not inflated data... within the time frame that you are looking at, some of the same users came in first via Google then later via Facebook (or vice versa), at the time of their visit, they were put into the appropriate channels...
But they are still the same user, and therefore the total is de-duplicating the same user.
For a simple example, let's say that I am visiting your site.
My first visit I came from Google, therefore in the "Google" channel I will count as "1 UV"
My second visit, I came from Facebook, therefore I will now also be added to the "Facebook" channel and I will count as "1 UV" there.
Now I come again to your site a third time, let's say this time I came from a marketing email, I will now be added to the "Marketing Email" channel, and yet again, I will be counted as "1 UV" there.
So:
Google 1
Facebook 1
Marketing Email 1
But when you look at the total for the month (or whatever time frame you are checking) I am still only 1 person.. I shouldn't be counted in the total 3 times.. therefore, the total will still be "1 UV"