Disk usage discrepancy?

You are referencing the section of the dashboard right?
So these must be the same that are found in the API, correct?

So when I check those I still find that the online intervall hours come to play here: i take the total storage summary and divide them by the average and this results in (my case) 417 which is the sum the displayed interval hours.

So no, it does not seem like this comes directly from the satellites.