REST API get reservation resources allocated

I need to know the resource allocated in a given reservation, but when I call the API URL:

https://vraHost/reservation-service/api/reservations/$$reservationId$$

I get TotalSize, ReservedSize, but not the allocated size of a resource.

I need the "This reservation allocated" values shown in the "Reservation Details -> Resoruces" screen as you can see in the following screenshot:

How can I get this values from the REST API?

Thanks a lot,

D.