BUG in DataBind? After .DataBind there are more DataGrid Items than DataSet Rows!

[Michael]

Consider:

Private Sub BindData(ByRef objDataSet As DataSet)
Dim x% = DataGrid_Report.Items.Count()
Dim y% = objDataSet.Tables(0).Rows.Count()
' Bind to the DataGrid
DataGrid_Report.DataSource = objDataSet.Tables(0)
DataGrid_Report.DataBind()
x = DataGrid_Report.Items.Count
y = objDataSet.Tables(0).Rows.Count()
' Format the checklist
Call Format_Checklist(objDataSet)
End Sub

The top x and y are initially both 18, yet after the .DataBind, y = 18
and x = 20. How can this be? Is this a bug in the DataBind method?
The xml for the DataSet looks good. What can I do to investigate
further??