Is that a ESX 4.x server then ? Since you mention COS.
There are other components that have CPU resources allocated/reserved.
What exactly do you want to report on ?
There is what is consumed and to what a VM is entitled to use
Get-VMHostMyEsx|Get-VM|
SelectName,
@{N="CPU Usage";E={$_.ExtensionData.Summary.QuickStats.OverallCpuUsage}},
@{N="CPU Entitlement";E={$_.ExtensionData.Summary.QuickStats.StaticCpuEntitlement}}