What is considered "Upload Space"?

My account keeps telling me that I am out of "upload space". I have been deleting any form submissions that I receive, after downloading them, but this message doesn't go away. What is being stored in this "upload space"?

Hi nia_garcia, thank you for reaching us.

Upload Space is referring to your forms that use a file upload field. The submissions can have file attachments on them and these files will take up the "Upload Space" limit. Please note that this does not reset, this is fixed. If you wish to free up your upload space, you can delete submissions that have file uploads on them, but please do keep in mind that deleting submission data is irreversible and will permanently remove the data in our servers.

However, I see that you only have 1 upload attachment. I have recalculated your Upload Space from our end. It should fix the over-limit issue.