Compute Savings Plan coverage

Hello.

I thought the explanation given in the document below might be relevant.
I thought that since discount rates are applied in descending order of magnitude, some discount rates may not be applied depending on the amount of commitment.
https://docs.aws.amazon.com/savingsplans/latest/userguide/sp-applying.html

We calculate your potential savings percentages of each combination of eligible usage. This percentage compares the Savings Plans rates with your current On-Demand rates. Your Savings Plans are applied to your highest savings percentage first. If there are multiple usages with equal savings percentages, Savings Plans are applied to the first usage with the lowest Savings Plans rate. Savings Plans continue to apply until there are no more remaining usages, or your commitment is exhausted. Any remaining usage is charged at the On-Demand rates.

For billing-related questions, I recommend opening a case with AWS Support under "Account and billing."
Inquiries under "Account and billing" can be made free of charge.
https://docs.aws.amazon.com/awssupport/latest/user/case-management.html