Size Discrepancy Between /drives & /root Endpoints

To preface this post, please view the below link.

https://learn.microsoft.com/en-us/answers/questions/1257868/microsoft-onedrive-drive-size-is-different-in-driv

When retrieving the total size of a drive via the /drives endpoint - one gets a response as follows.

{
  "deleted": 3143,
  "remaining": 212025579370,
  "state": "normal",
  "total": 1099511627776,
  "used": 887486045263
 }

When retrieving the same drive via its /drives/{id}/root endpoint - it returns the following metric.

"size": 75217259136

The 'used' metric matches the Microsoft Admin Center OneDrive usage panel. The 'size' metric matches the actual downloaded size of the drive.

What is the cause for a discrepancy of 800 GB? A response to the other post details, "The difference between the two values is the additional space used by the system." Could I have some specifics of where I could acquire this system data (or at the very least view some metadata for it)?

Thanks!