Sometimes you may not be able to examine certain folders, because you don’t have sufficient access permissions. For example, certain system folders and folders of other local users are normally inaccessible, even when you are logged in to your Mac as an administrator.
Such folders will appear empty and of zero size in DaisyDisk. Their actual size will be therefore included into the hidden space.
In such cases you can use the scan as administrator command.
Sometimes you may not be able to delete certain files and folders because you don’t have sufficient write access permissions (while read access may be available). For example, apps in /Applications are often protected from deletion with the additional password box.
In such cases, DaisyDisk automatically attempts to raise its deletion permissions, when possible.