When reporting on any 'unique' Metric (e.g. visitors or page views), we always give an overall total that represents the number of unique visitors or unique page views over the chosen reporting period.
But on the some of the Reports or CSV exports, we also provide daily roll ups that show the number of unique visitors / page views that occurred on each day. Because the same unique visitor or unique page view could be tracked multiple times across a reporting period spanning multiple days, adding each of these daily data points up will likely not match the overall total number over the entire reporting period.
To Illustrate this, here is a simple example with 2 users, Joe and Jane, who visit the hub across 3 days and we'll look at Unique Visitors (of course you're Hub is going to get a lot more traffic than that!):
Day 1: Joe Visits Hub
Day 2: Joe and Jane Visit Hub
Day 3: Jane Visits Hub
Now if we are reporting on the number of unique visitors from Day 1 to Day 3, clearly the overall total is 2 (Joe and Jane), but the daily data points that would show on a graph or CSV export will not sum up to 2:
Day 1 = 1 (Joe)
Day 2 = 2 (Joe and Jane)
Day 3 = 1 (Jane)
If you were to sum up each day, the figure would be 4, which is not the total number of unique visitors for the 3 days. We know only Joe and Jane visited our Hub during those 3 days.
So because we must display the 'unique' Metrics data in 2 different ways, the sum of all the daily data points will most likely not equal the overall total of uniques for the entire reporting period.
If you have any questions on this, please contact the Success Team!