docs: function onData( subtrahend ) {
  		/**
  		* FUNCTION: onData( newVal, encoding, clbk )
  		*	Data event handler. Performs subtraction.
  		*
  		* @private
  		* @param {Number} newVal - streamed data value
  		* @param {String} encoding
  		* @param {Function} clbk - callback to invoke after performing subtraction. Function accepts two arguments: [ error, chunk ].
  		*/
  		return function onData( newVal, encoding, clbk ) {
  			clbk( null, newVal-subtrahend );
  		}; // end FUNCTION onData()
  	}