Bin visible in Storage overview, even when Trash is emptied
My Macbook Air (2015) running macOS Catalina has a problem with the trashcan. The bin (far down right) is empty and opening it shows an empty bin, but according to "Storage" (Apple Icon top left → About This Mac → Storage) there is over 30 GB of trash still on my Mac. With the System Information application, I've found the name of the folder, but its contents are all locked, even though I am the sole user of my Macbook Air.
My question is how to delete this 'additional' trash from my Mac