I have had to ask a member of the development team for help with your question and this was the answer fro the column [Cluster_SqlServer_Process_CumulativeUserTime]
In the case of the data.cluster_sqlserver_process_unstablesamples_view the CumulativeUserTime is the amount of time the process has spent in ‘user mode’ (as opposed to kernel, or privileged mode). If you compare the cumulative user time from one second to the next, you can work out how much time the process has been working for. So if the difference was 0.75 seconds between 1 second pollings, you’d know it has been using 75% of the CPU (although this is offset by multi core, etc, etc.).
So, I'm not really sure if that helps at all?