Sudden increase in use labeled "backup" I never asked for. Where can I delete?

Hello,

I have less than 2GB in my actual Dropbox folder. All of a sudden, I was warned my space is full. I checked the website and in account management there is almost 6GB labeled as "backup". Yet I have never once selected to backup anything, I only ever wanted the folder. But my real question is this, how do I delete the unwanted data? Again, in my folder, both online and in my PC, are under 2GB. The only answers I ever found were the generic Settings>Backup>Manage backup, but when I do that, it opens the wizard for first time backing up, asking which folders I want to back up. None are actually backed up. Thank you for any help.