Can't delete some files from Clip Sport

I downloaded a bunch of mp3 files into the audiobooks folder with other files in a nonsupported format. I deleted them using my computer but the files still show in the audiobooks folder. How do I delete those from the clip sport? They do not show up when I look at audiobooks folder using my computer.

The files show when I go Folder/Internal Memory/Audiobooks

But if I go Books/Audiobooks the files don’t show up in the list.