Hi Cho,
You need to set the axis View - for example:
   NChart chart = nChartControl1.Charts[0];

    NLineSeries line = new NLineSeries();
    chart.Series.Add(line);
    Random rand = new Random();

    line.UseXValues = true;
    line.DataLabelStyle.Visible = false;

    for (int i = 0; i < 40; i++)
    {
      line.Values.Add(rand.Next(100));
      line.XValues.Add(i);
    }

    chart.Axis(StandardAxis.PrimaryX).View = new NRangeAxisView(new NRange1DD(0, 100), true, true);
    chart.Axis(StandardAxis.PrimaryX).ScaleConfigurator = new NLinearScaleConfigurator();
this will allow you to set a different range than the one that is automatically calculated based on the chart content. Let us know if you have any questions.

Best Regards,
Nevron Support Team