You may notice that Uptime Infrastructure Monitor memory values do not match those shown in the VMware Virtual Infrastructure Client memory graph. This is because Uptime Infrastructure Monitor collects a different metric to represent ESX host memory usage than what is displayed in the default VMware graph.
Uptime Infrastructure Monitor collects the Memory Unreserved (Average) from the VMware ESX API. To see this value in the Virtual Infrastructure Client, click Performance for your target ESX host and then select Memory from the available graphing dropdown list. Click Change Chart Options and select the Memory Unreserved (Average) series.