Managed Backups

Hi,
On this site, as on many others, the size of my managed backups started to balloon recently. I have cleaned all the junk off the server, excluded all sorts of backup and export plugin folders that had big files, and rerun the managed backups, and they are still huge compared to a few weeks ago and I have added nothing to the site.
What does managed backup function actually backup? Does it pay attention to the exclusions in the settings?
Thanks!