The cost of licensing for Azure Red Hat OpenShift can be a bit complex, so I'll do my best to explain.
When you purchase Azure Red Hat OpenShift, you are required to pay for both the infrastructure costs. the virtual machines, storage, and networking resources) and the software licensing costs (i.e. the Red Hat OpenShift subscription). The software licensing costs are based on the number of application nodes and the instance type, and type and are separately from the infrastructure costs.
If you choose to purchase Reserved Instances for the virtual machines, you will receive a discount on the infrastructure costs. However, Reserved Instances do not apply to the software licensing costs. So even if you purchase Reserved Instances for the virtual machines, you will still need to pay the full software licensing costs, which may include an upfront payment and monthly payments.
It's possible that the Azure calculator is not accurately reflecting the cost of the software licensing, or that there is a glitch in the calculator. I would recommend double-checking the pricing details for Azure Red Hat OpenShift to ensure that you are getting an accurate estimate.
You may also want to consider reaching out to Microsoft support or a qualified Azure partner to get more information on the pricing and licensing options for Azure Red Hat OpenShift, and to get help with estimating the costs for your specific use case.
If this does answer your question, please accept it as the answer as a token of appreciation.