code: function (group) {
              var options = this.options,
                formatOption = options.format,
                str = formatOption ?
                  format(formatOption, this) :
                  options.formatter.call(this);  // format the text in the label
  
              // Change the text to reflect the new total and set visibility to hidden in case the serie is hidden
              if (this.label) {
                  this.label.attr({text: str, visibility: HIDDEN});
                  // Create new label
              } else {
                  this.label =
                    this.axis.chart.renderer.text(str, null, null, options.useHTML)		// dummy positions, actual position updated with setOffset method in columnseries
                      .css(options.style)				// apply style
                      .attr({
                          align: this.textAlign,				// fix the text-anchor
                          rotation: options.rotation,	// rotation
                          visibility: HIDDEN					// hidden until setOffset is called
                      })
                      .add(group);							// add to the labels-group
              }
          }
docs: Renders the stack total label and adds it to the stack label group.