How increase instance storage for r6gd.xlarge

Hello.

The volume size of instance store volumes is determined by the instance size.
So, if you want to increase the size, I think you need to increase the instance size.
By the way, please note that data on instance store volumes will be deleted if EC2 is stopped.
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/InstanceStorage.html#instance-store-volumes

The number, size, and type of instance store volumes are determined by the instance type and instance size. Some instance types, such as M6, C6, and R6, do not support instance store volumes, while other instance types, such as M5d, C6gd, and R6gd, do support instance store volumes. You can’t attach more instance store volumes to an instance than is supported by its instance type. For the instance types that do support instance store volumes, the number and size of the instance store volumes vary by instance size. For example, m5d.large supports 1 x 75 GB instance store volume, while m5d.24xlarge supports 4 x 900 GB instance store volumes.