That is NOT a copy of the clips. It is a symlink.
Note the small size, and note the little hook arrow in the icon.
Two things you may want to do.
1) Actually save possibly a lot of space by deleting all generated files. Odds are that these will save you a lot more than the originals. Select the library in the browser sidebar, and do File->Delete Generated Library Files...
Check everything, including All Render Files.
2) To make sure that files are not lost, you may want to "Consolidate", that is, make sure that all the media is safely stored inside the library. This will actually COPY the external files to that location inside the library.