There are three primary way to reduce the space on a backup account.
1. Manually delete data from the account.
2. Set a retention policy on the Online Backup and Recovery Manager
3. Use the cleanup tool to mass remove data from a backup account
How to delete data from the cloud to reduce the used space
Please refer to the following article on how to to delete data from a backup account
How to set a retention policy
A retention policy can be set to automatically delete data from the cloud-based on certain conditions to manage the space in the cloud.
Refer to the following article for steps on how to set a retention policy on the Online Backup and Recovery Manager
How to remove or limit file version stored in the Cloud
The account cleanup tool can be used as a option to mass delete data that has not been backed up for a specified amount of time.