code: def _reductionForOffset(self, offset):
          
          reduction = 0
          for (thisOffset, thisReduction) in self._adjustments:
              if offset >= thisOffset:
                  reduction += thisReduction
              else:
                  break
          return reduction
docs: Calculate the total reduction for a given X axis offset.
  
          @param offset: The C{int} offset.
          @return: The total C{float} reduction that should be made for this
              offset.