The SUM clause establishes a Report Writer sum counter and names the
  data items to be summed.

  Format -

   {SUM {sum-name}...
       [UPON {detail-report-group-name} ... ]} ...

       [RESET ON { control-foot-name } ]
       [         { FINAL             } ]

  Additional Information (explode) :

• sum-name
• detail-report-group-name
• control-foot-name