You can try use special setting for shows sume value yAxis.stackLabels on stacked series. , but it is a setting that shows the sum of column values. To get the maximum value, you should dig into the core and create a wrapp extending-highcharts.

Highcharts.chart('container', {
  chart: {
    type: 'column'
  },
  plotOptions: {
    column: {
      stacking: 'normal',
    }
  },

  yAxis: {
    allowDecimals: false,
    min: 0,
    title: {
      text: 'Number of fruits'
    },
    stackLabels: {
      enabled: true,
            verticalAlign: 'bottom',
      style: {
        fontWeight: 'bold'
      },
      formatter: function() {
        var val = this.total;
        if (val > 0) {
          return val;
        }
        return '';
      },

    }
  },
  series: [{
      data: [4, 3, 5, 6, 2, 3]
    },
    {
      data: [4, 3, 5, 6, 2, 3].reverse()
    }
  ]

});

Demo: https://jsfiddle.net/BlackLabel/80dcmj2e/1/