The reported used space by your node (signed orders) maybe different from the physically used space for a lot of reasons, described above, and also (mostly), that the filewalker didn’t finish its job and didn’t move the garbage to the trash.
You need to search for errors, related to gc-filewalker, lazyfilewalker and retain in your logs and possible fix them.
If all filewalkers working without issues, the discrepancy should be a few percents.
P.S. I do not think, that generating more topics for the exact same problem will speedup a process to fix it.