The automatic backups split the files into the same individual backups as the manual backups i.e. "Themes", "Plugins", "Uploads" and "Others".
Since you can only see Uploads and Others listed in Existing Backups, UpdraftPlus isn't backing up Themes or Plugins.
If you go to the settings tab, under "Include in files backup", are the Themes and Plugins checkboxes checked? If not, check these and they should be included in future backups.