You may notice alerts from the ESX Workload monitor indicating that the Percent Used for a specific VM instance is greater than 100%. This is a valid scenario alerting that the instance is using more than its entitlement of CPU resources.
Example:
Notification type: Problem 23/Jun/2010 08:31
Host: esx01 (OK)
Service: ESX hosts monitor (member) Service State: CRIT
Output: Percent Used: 103.8% >= 75%