Retrieve Total System Storage Size For Premium Capacity Via Rest API, or functions

It would be highly beneficial to have a feature (REST API) that allows us to retrieve the total system storage size of all items within Premium capacity. Currently, we need to regularly check the overall usage, but there is a discrepancy between the "Item Size (GB)" shown in the Microsoft Fabric Capacity Metrics app and the actual system storage size of the semantic model. Therefore, there is a demand for accurately verifying the system storage size.