highcharts round generated y labels in 1024 multiply not 1000

I have a chart with sample data: [1462218035, 2079623792, 2146097338, 2169087177] and in y axis label i convert it to human readable bytes:

yAxis: {
    labels: {
    useHTML: true,
    formatter: function () {
        return bytesToReadable(this.value, true);
    },
  },
}

bytesToReadable converts bytes to human readable data: 1,36 GB - 1,94 GB - 2 GB and it shows y labels like: 953,67 MB - 1,86 GB - 2,79 GB those are 2,000,000,000 - 4,000,000,000 - 6,000,000,000 converted by bytesToReadable. What i want is 2,000,000,000 - 4,000,000,000 - 6,000,000,000 generated by highcharts to be multiply of 1024 to be correct numbers after convert like 100 MB - 1GB - 4GB.