How vCloud Director calculate the CPU used reservation

We have use the vCloud Director to create vApp, but some virtual machine can not be started due to CPU limitation with NO_FEASIBLE_PLACEMENT_SOLUTION error and no vSphere task triggered. Actually, the vSphere cluster still have enough resource to start the VM, we can manually start the VM at vCenter.

We found that at the allocation page of the organization vdc properties, it said the use reservation of CPU has reached 83% of the total. According to our setting on vSphere cluster admission control with 17% CPU reservation, maybe it burn out the CPU resource on the cluster. It make sense to VM power off failed.

But we are confused:

1. How vCloud to verify the CPU resource in the organization, why we can start the VM but failed in vCloud?
2. How vCloud to calculate the CPU used reservation? We count all the used CPU and reservation of VM that under the organization vdc, the number is much lower than  used reservation that vCloud showed.
3. We have set some VMs with high latency sentivity, does it has impact and How
   

We use vCloud Director 8.10 vCenter 6.0 .0.