It might take some time for the deleted image to be completely removed from the Glide storage, and you should also make sure the link isn’t referenced anywhere else.
Your uploads consume the storage quota, I think that’s what they mean.
Is it a folder you created before the teams migration?
I have already moved all my apps out of the my apps folder into team folders. But some of the teams are legacy team is. It was my understanding that they were gonna be doing all of those. I saw a message from somebody Is at Glide saying that they were gonna do it over a weekend.