Vmware Memory using SNMP

I am reading the VMWare Resources MIB to monitor memory on my ESX

server.  I reading these three OIDS:

Total Memory>.1.3.6.1.4.1.6876.3.2.1

Used Memory>.1.3.6.1.4.1.6876.3.2.2

Free Memory>.1.3.6.1.4.1.6876.3.2.3

The total memory matches what I see in the Virtual Infrastructure

Client, but the Memory Usage does not match what I see in the MIB for

Used Memory.  Any thoughts what the MIB is actually looking at?  Any

idea where can get the information in the Client from SNMP?