s3SubPrefix
The S3SubPrefix is appended to the location scope creating the grant scope. Use this field to narrow the scope of the grant to a subset of the location scope. This field is required if the location scope is the default location s3:// because you cannot create a grant for all of your S3 data in the Region and must narrow the scope. For example, if the location scope is the default location s3://, the S3SubPrefx can be a /*, so the full grant scope path would be s3://<bucket-name>/*. Or the S3SubPrefx can be <bucket-name>/<prefix-name>*, so the full grant scope path would be or s3://<bucket-name>/<prefix-name>*.
If the S3SubPrefix includes a prefix, append the wildcard character * after the prefix to indicate that you want to include all object key names in the bucket that start with that prefix.