Dear Learner,

We hope you are doing well.

If you have launched 3 instance and all the 3 instance runs for whole day means 24 hrs * 3 = 72 hrs are consumed, in the same way if those 3 instance for whole month then 72 * 30 = 2160 hrs are consumed and aws provide the free limit of 750 hrs per month only so that's you are getting charged for the instances.

To avoid the bill please stop the instance once you are done with your practical part.

Feel free to contact us in case you have any query.