I am having an even more drastic example like yours.
I am currently investigating, so I can’t tell yet why I am seeing this:
A 16TB partition says it is 100% full on Linux df -H. But the node dashboard says it has only around 8TB of node data on it.
As said, I am currently trying to figure out where does that discrepancy come from.
You could do a du -sh to have the folder sizes on disk calculated but it might take some time.
Ncdu might also give some insights: NCurses Disk Usage