The kernel mode time is the amount of time the process(es) run by the job spent executing in kernel mode. 

Processor times include only steps that execute ProgramExecutionTasks, ScriptTasks, and CustomTasks. Processor time is not recorded for other tasks. 

Processor times reflect the amount of CPU time used by the job, and will not equal actual elapsed time for the job. 

This value includes all instances of the job, including those whose ExecutionHistoryItems have been purged. To reset this value use Job.ClearHistory.