Total DPC Time is the average percentage of time that all processors spend receiving and servicing deferred procedure calls ...

% Total DPC Time is the average percentage of time that all processors spend receiving and servicing deferred procedure calls (DPCs).  (DPCs are interrupts that run at a lower priority than the standard interrupts). It is the sum of Processor: % DPC Time for all processors on the computer, divided by the number of processors.  System: % Total DPC Time is a component of System: % Total Privileged Time because DPCs are executed in privileged mode.  DPCs are counted separately and are not a component of the interrupt count.  This counter displays the average busy time as a percentage of the sample time.