Unable to figure out required (to be deleted) Documents as information is not consistent I am trying to free up some space (around 20GB) in order to install Big Sur on my 2019 Air, 128GB.
Under Storage Management, I select Documents that are shown to occupy 36GB of space. However, there are no Large Files, Downloads, or Unsupported Apps. When I click the File Browser option, the files and folders listed don't sum up to the size mentioned in the Recommendations.
The pic below showcases my situation:
This file size discrepancy most likely occurs due to hidden files in the user/library folder.
To show hidden files, open a Finder window and hit shift cmd .. You will immediately see that these files are shown with grey text in finder.

However, be careful with deleting these, you can harm the system or programs by doing so.