code: function(index) {
          var sum = 0;
  
          $.each(this._sizes, function(i, value) {
              if (i < index) {
                  sum += value.totalSize;
              }
          });
  
          return sum;
      }
docs: Calculate the size to cycle width based on the sum of all items up to but not including the defined index.
  
  @param {Number} index    - Includes the clone index
  @returns {Number}
  @private