Egomuzun nasıl bir sorun oluşturduğunun farkında mıyız? Anlamak için güzel bir video.
https://www.youtube.com/watch?v=B2SqA83xMLk

Devexpress,xtragrid,summaryItem bilgilerine ulaşmayla ilgili not.

When you ungroup the Organization column, the TotalSummary calculation starts again. And this time, the GridColumn.SummaryItem.SummaryValue property of the Value 1 and Value 2 columns contains previous calculation values.
The order of TotalSummary calculation depends only on the order in which columns were added to the GridView.Columns collection and a developer should set this order.
You can change this order at runtime. For this, select all columns that have the GridColumn.SummaryItem.SummaryType property equal to SummaryItemType.Custom and delete them from the GridView.Columns array. Then, add them to the end of this array. Modify your Form.Load event handler as shown below:

[C#]
private void Form1_Load(object sender, EventArgs e) {
    this.gridControl1.DataSource = CreateDataSource().Tables[0];
    List<DevExpress.XtraGrid.Columns.GridColumn> customSummaryColumns = 
    this.gridView1.Columns.Where(c=>c.SummaryItem.SummaryType == DevExpress.Data.SummaryItemType.Custom).ToList();
    foreach(var column in customSummaryColumns) {
        gridView1.Columns.Remove(column);
        column.Visible = true;
        gridView1.Columns.Add(column);
    }
}