code: function () {
              var carousel = this,
                  isVertical = carousel.get("isVertical"),
                  cols       = carousel._cols,
                  item     = carousel._firstItem - carousel.get("numVisible");
  
              if (item < 0) { // only account for multi-row when scrolling backwards from item 0
                  if (cols) {
                      item = carousel._firstItem - cols;
                  }
              }
  
              if (carousel.get("selectOnScroll")) {
                  carousel._selectedItem = carousel._getSelectedItem(item);
              }
  
              carousel.scrollTo(item);
          }
docs: Scroll the Carousel by a page backward.
  
  @method scrollPageBackward
  @public