It deletes it from all of your relays, any additional ones you have to enter manually.

But with it it being very old that should take care of it.

But yeah, it isn't 100.

Deleting on nostr is iffy at best 🤷

Best way to control the images in posts is to use a nostr.build account and upload the images there first and then copy the links into the post.

Then you are able to delete image at the source.