AWS Backup DynamoDB billing

Hi everyone! I'd like to understand better the billing composition regardless of AWS Backup on DynamoDB resources since I got an unexpected increase in my billing.

I'm aware of AWS Backup billing itself thanks to the documentation, anyway, when I access the Billing service I can notice an exponential billing pricing in DynamoDB service, on the section Amazon DynamoDB USE1-TimedBackupStorage-ByteHrs the description allows me to see that I'll be paying $0.10 per GB-month of storage used for on-demand backup, showing me that I've used 14,247.295 GB-Month (This makes sense with the billing I got) but where my doubt comes from is, where does all those GB come from? The last snapshot-size just shows 175.5 GB

I've configured my backup plan with the following parameters:

{
    "ruleName": "hourly-basis",
    "scheduleExpression": "cron(0 * ? * * *)",
    "startWindowMinutes": 60,
    "completionWindowMinutes": 180,
    "lifecycle": {
        "toDeletedAfterDays": 30
    }
}

I'm also copying snapshots into a second region on us-west-2

As you can see, I'm handling a schedule expression on an hourly basis backup because of compliance requirements. Is this enough justification for the high billing? I'm aware that backups with low RPO are commonly expensive but I just want to be sure that this billing is not higher than it should be because of any wrong Backup configuration.

Thanks in advance!