SharePoint Storage Reporting. Which result is the most reliable

Once again, due to versioning of files, we've run out of storage space on our SharePoint Online site. We've had warnings that people won't be able to save new work (but I haven't actually noticed anyone actually experiencing that yet.)

I'd just like to be clear which 'totals' are the most accurate,up to date and what they actually refer to.

There's

(a) the total in the top right of the "Active Sites" panel. 

(b) the sum of the column " Storage used" in the "Active Sites" Panel
(c) by totaling up the results of every site by taking the sum of all entries in each site collections "Storage Metrics" I suspect this is the most accurate and up to date but seems like a lot of work.

(Please let me know if there's others.)

• What aren't these three values ever the same?
• Are they counting the the same metrics?
• If there's a delay for one result to catch up, typically how long is this delay?
• Which of these results is reporting
  i) Active Files
  ii) Versioned Files
  iii) Recycle Bins
  iv) Second Stage Reycle bins.
  v) Preservation Hold or other retention libraries.

Is there any way I can get a report of the above as separated out results?

What result is Microsoft looking at when they say issues a warnings that we're out of space?

Everything just seems a little bit arbitary.