update details for max allocated storage

website/docs/r/db_instance.html.markdown

@@ -357,7 +357,7 @@ docs](http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_UpgradeDBInstan
 for more information.
 * `manage_master_user_password` - (Optional) Set to true to allow RDS to manage the master user password in Secrets Manager. Cannot be set if `password` is provided.
 * `master_user_secret_kms_key_id` - (Optional) The Amazon Web Services KMS key identifier is the key ARN, key ID, alias ARN, or alias name for the KMS key. To use a KMS key in a different Amazon Web Services account, specify the key ARN or alias ARN. If not specified, the default KMS key for your Amazon Web Services account is used.
-* `max_allocated_storage` - (Optional) When configured, the upper limit to which Amazon RDS can automatically scale the storage of the DB instance. Configuring this will automatically ignore differences to `allocated_storage`. Must be greater than or equal to `allocated_storage` or `0` to disable Storage Autoscaling.
+* `max_allocated_storage` - (Optional) Specifies the maximum storage (in GiB) that Amazon RDS can automatically scale to for this DB instance. By default, Storage Autoscaling is disabled. To enable Storage Autoscaling, set `max_allocated_storage` to **greater than or equal to** `allocated_storage`. Setting `max_allocated_storage` to 0 explicitly disables Storage Autoscaling. When configured, changes to `allocated_storage` will be automatically ignored as the storage can dynamically scale.
 * `monitoring_interval` - (Optional) The interval, in seconds, between points
 when Enhanced Monitoring metrics are collected for the DB instance. To disable
 collecting Enhanced Monitoring metrics, specify 0. The default is 0. Valid