code: function (xOffset, xWidth) {
              var stackItem = this,
                axis = stackItem.axis,
                chart = axis.chart,
                inverted = chart.inverted,
                neg = this.isNegative,							// special treatment is needed for negative stacks
                y = axis.translate(axis.usePercentage ? 100 : this.total, 0, 0, 0, 1), // stack value translated mapped to chart coordinates
                yZero = axis.translate(0),						// stack origin
                h = mathAbs(y - yZero),							// stack height
                x = chart.xAxis[0].translate(this.x) + xOffset,	// stack x position
                plotHeight = chart.plotHeight,
                stackBox = {	// this is the box for the complete stack
                    x: inverted ? (neg ? y : y - h) : x,
                    y: inverted ? plotHeight - x - xWidth : (neg ? (plotHeight - y - h) : plotHeight - y),
                    width: inverted ? h : xWidth,
                    height: inverted ? xWidth : h
                },
                label = this.label,
                alignAttr;
  
              if (label) {
                  label.align(this.alignOptions, null, stackBox);	// align the label to the box
  
                  // Set visibility (#678)
                  alignAttr = label.alignAttr;
                  label[this.options.crop === false || chart.isInsidePlot(alignAttr.x, alignAttr.y) ? 'show' : 'hide'](true);
              }
          }
docs: Sets the offset that the stack has from the x value and repositions the label.