Zabbix vmware cpu usage values do not match values from vCenter

The CPU usage values from vmware.hv.cpu.usage do not match the values observed directly from vCenter and vmturbo. The numbers do not match, and the values are displayed as if they only change approximately every half hour. I have tried different sampling frequencies and am currently getting data every 60 seconds.

If this is due to slow response time, getting values from vmware, how do I determine that?