The usage meter records virtual RAM usage, not physical to the host, with a 50% minimum based on what is configured for the virtual machine Example: If the virtual machine is configured with 4096 MB RAM and no reservation, the usage meter will record 2048 or 50% at collection time. If the reservation is above 50% allocated vRAM, then that value is the amount recorded at collection time. The easiest place to see this is with the Detailed Billing Report where is shows the allocated/configured virtual RAM and the billing amount.
The only place where this rule is not completely followed is with vCloud Director Reservation allocation models since the customer can have more control over shares and memory reservations. With Reservation allocation models, we will bill virtual RAM usage for virtual machines up to the memory limit for the resource pool that backs the Reservation org VDC (Go to vCenter, find a resource pool that packs and Reservation org VDC, look at settings and memory limit).
