RadChart XAxis steps

[Sonia]

I have used XAxis steps to ensure that ticks are placed every 1 step.

ChartSeries serieIndicator = new ChartSeries("Indicator") { Type = ChartSeriesType.Line };

serieIndicator.Items.Add(new ChartSeriesItem(0, 47));
serieIndicator.Items.Add(new ChartSeriesItem(1, 35));
serieIndicator.Appearance.PointMark.Visible = true;
serieIndicator.Appearance.PointMark.Border.Width = 2;
serieIndicator.Appearance.PointMark.Border.Color = Color.RoyalBlue;
serieIndicator.Appearance.PointMark.Dimensions.AutoSize = true;
serieIndicator.Appearance.PointMark.Dimensions.SetDimensions(new Dimensions(6, 6));
serieIndicator.Appearance.PointMark.Dimensions.AutoSize = false;
serieIndicator.Appearance.PointMark.FillStyle.MainColor = Color.White;
serieIndicator.Appearance.PointMark.FillStyle.FillType = FillType.Solid;

RadChart1.Series.Add(serieIndicator);

RadChart1.PlotArea.XAxis.AutoScale = false;
RadChart1.PlotArea.XAxis.Step = 1;

ChartSeries serieObjective = new ChartSeries("Objective") { Type = ChartSeriesType.Line };
serieObjective.Appearance.PointMark.Visible = true;
serieObjective.Appearance.PointMark.Border.Width = 2;
serieObjective.Appearance.PointMark.Border.Color = Color.RoyalBlue;
serieObjective.Appearance.PointMark.Dimensions.AutoSize = true;
serieObjective.Appearance.PointMark.Dimensions.SetDimensions(new Dimensions(6, 6));
serieObjective.Appearance.PointMark.Dimensions.AutoSize = false;
serieObjective.Appearance.PointMark.FillStyle.MainColor = Color.White;
serieObjective.Appearance.PointMark.FillStyle.FillType = FillType.Solid;
serieObjective.Items.Add(new ChartSeriesItem(0, 20));
serieObjective.Items.Add(new ChartSeriesItem(1, 40));
serieObjective.Items.Add(new ChartSeriesItem(2, 60));
serieObjective.Items.Add(new ChartSeriesItem(3, 80));

RadChart1.Series.Add(serieObjective);

However I cannot understand the resulting chart.
Why seven steps if i only created chartseriesitem from 0 to 3?

Thanks for your help,
Sonia.

[Sonia]

I discovered this can be forced by setting the min and max value.

RadChart1.PlotArea.XAxis.MinValue = 0;
RadChart1.PlotArea.XAxis.MaxValue = 3;