If you still having issue with your limited storage space:
Simple:
1. Download your old backup/s equivalent of 35.63 GB as tar format to your own PC.
2. Delete them from Plesk after download to free the required space.
3. Start backing up again.
4. Delete the Plesk local copy after completion.
As Igore mentioned, Plesk Backup Manager cannot backup your files directly to Google Drive, it must create a local copy first.