You can modify an AS group as needed. The values of the following parameters can be changed: Name, Max. Instances, Min. Instances, Expected Instances, Cooldown Period, Health Check Method, Health Check Interval, Health Check Grace Period, Instance Removal Policy, EIP, and Notification Mode.
Changing the value of Expected Instances will trigger a scaling action. Then, AS automatically increases or decreases the number of instances to the value of Expected Instances.
If the AS group is not enabled and does not contain any ECS instances, and no scaling action is being performed, you can also modify AZ, Subnet, and ELB configurations.
Click Modify in the upper right corner of the Basic Information page.
You can also locate the row containing the target AS group and choose More > Modify in the Operation column.