Best way to get value of performance monitor via REST api?

Best way to get value of performance monitor via REST api?

In OpManager 11 what is the best way to get the last polled value of a single performance monitor?  I'm looking at using getAssociatedMonitors call and parsing out what I need, i.e. the time and value.  Is there a better way to do this? 
 
I did look at getGraphData but it wasn't clear to me what the x values represented.  They look to be timestamps, but I'm not sure what offset they are using (it doesn't appear to be the epoch).

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