Sets or returns the x coordinate of the upper left corner of the chart region, in units of 1/4000 of the chart area.

 public int X{ get; set; }

Public Property X() As Integer

For SeriesDataLabel, the origin for the X coordinate is the "Default" location for the data label.
If you set X to a value that would put the Chart region off the chart, then when the workbook writes, the value will be clamped such that the region will still appear on the chart.