我有一个新的 AWS 账户，在主要用于 EMR 的同一区域中预留容量为 15 个相同实例类型的 EC2 实例。
如果我在 15 天内生成一个包含 10 个实例的 EMR 集群，并在剩余的 15 天内将其扩展到 20 个实例，我会收取 0 美元的费用吗？
如果没有，该月 EC2 的最终账单将如何计算？
我感到困惑的原因是，根据我的理解，EC2 收费是基于消耗的容量（以实例小时计）而不是实际分配的实例。由于我要保留 15 个实例的容量，我预计它总共会花费我 0 美元，因为我的每月平均消耗量值 15 个实例。
预留 EC2 定价文档和 Internet 上的大多数 AWS 价格计算相关材料都没有提到在具有预留容量的账户中动态扩展实例的用例。
Reserved instances are applied to running instances in real time, not averaged over any longer period of time. They are baseline, not average.
For example, if you own three Reserved Instances with the same instance attributes and region (or Availability Zone if applicable), the billing system checks each hour to see how many total instances you have running that match those parameters. If it is three or less, you will be charged the Reserved Instance rate for each matching instance running that hour. If more than three are running, you will be charged the On-Demand rate for the additional instances.
https://aws.amazon.com/ec2/pricing/reserved-instances/buyer/
At any instant in time when you lack enough reserved capacity to cover your running workload, you're billed for the excess.