Once you reserve an instance for a fixed term, you may want to stop using it or to exchange your instance for bigger or smaller ones. Assuming the conversion is made with the same instance type and this is done in the same AZ, a conversion factor can be applied using a normalization factor, take the following example:
One m1.xlarge can be changed for two m1.large, four m1.medium, and eight m1.small.
For more information about normalization factors and how RIs are applied use the following link: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/apply_ri.html.
Reserved Instances can also be resold in the AWS Marketplace so current reservations can be transferred to new owners and customers can find instances with shorter terms.