The relative file size display bar does not correctly show the relative size of the file

Isn't it strange that a file that's only 6kb has such a long blue bar?

Not strange at all. Turn off Preferences / Miscellaneous / Advanced: [Information Display] graphs_separate_files_dirs if you want files to be compared to folders here, instead of being separate. But it usually result in the files being tiny compared to the folders, which isn't that useful.