An extension of Azure for running apps in an on-premises environment and delivering Azure services in a datacenter.
That command looks correct to query the Provider Usage API, so it should be giving you the provider info (not be confused with the Tenant Usage API).
If you are including all Subscriptions (you will need to call for each one individually) and still seeing a difference your best bet is to create a support request so a detailed breakdown of the differences can be done.