How to see S3 backup size?

Hello. How can I see the size of a specific S3 backup? I have looked, in the AWS console Backup Dashboard at the Recovery Point under "Protected Resources", In the Backup Vault (in each Recovery Point), and in the Jobs history. This information (size and transferred bytes) is not shown in any of them. I have set up EventBridge and sending the logs to CloudWatch but the log events of both the "Recovery Point State Change", and the "Backup Job State Change", always show: "backupSizeInBytes": "0", "bytesTransferred": "0". I know for sure that the S3 bucket has changed since the last backup, new large objects (GBs) were added. So, I can't find a proof that the backups are actually doing anything and what is the size they occupy. I can't even see what is the size of the first, complete, backup. I have tried using the CLI to describe the recovery points and backup jobs the backupSizeInBytes is always 0.

Thanks.