Cannot account for Total Team Space

Good Day,

I manage dropbox for a team of around 100 accounts. We were happily using Dropbox Standard until dropbox indicated that my Team total usage is above 5TB limit for standard plan. I was then forced to upgrade to Dropbox advanced to keep the team going and allowing them access to there files.  

However I found this quite strange as we generally control our space between the users. Using the dropbox admin interface I can only account for 3TB of space and cannot for the life of me account for the extra 3TB+ that Dropbox claims I am using. I have had multiple discussions with Dropbox support where the agent end up conceding that the numbers look strange and they will have to escalate to an engineer, only to come back to a generic answer like "the space shown is the total of team folders, shared folders, backups, and root drives". 

Since Dropbox bills  me based on space consumed, I find it unacceptable that I cannot account for the space through my admin interface so that I can eventually manage and ask the correct team etc to check on what is going on. 

I have added up the totals shown in dropbox admin console, in "Members" Tab Plus the usage's shown under "Content->Team and Shared".

Question is, What am I missing? how can I account for all my space used when adding up the elements on the admin console does not come close to the total Dropbox claims we use.

Thanks