Data left after form upload deleted

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I have a site where there is a careers section, and candidates are asked via a form to upload their resume.

When I look at the "form results" tab and start deleting the job seekers responses the data is still left behind.

example found in:

whatever.com/files/3262/9545/8912/resume.pdf

all of the deleted forms (resumes) are still there.

how do I delete this, besides manually combing thru every individual folder (over 40 already)?