Personally, FileLight for me is unreliable | inaccurate.
Also, I assume you’re using BTRFS (I see .snapshots) ?
If yes, the default “df” is also not accurate with BTRFS.
Might read thru this:
https://archive.kernel.org/oldwiki/btrfs.wiki.kernel.org/index.php/FAQ.html#How_much_free_space_do_I_have.3F
.