Hi NewbApps,

you will have to set Custom Summary Name, in your case it should be something like:

 SummaryRow fs = WebDataGridPicklistBatch.Behaviors.CreateBehavior<SummaryRow>();

 
            //add default summaries
            if (!this.IsPostBack && fs != null)
            {
                ColumnSummaryInfo info1 = new ColumnSummaryInfo();
                info1.ColumnKey = "FGQuantity";
                Summary summary = new Summary();
    summary.CustomSummaryName = "Total FG ";
    summary.SummaryType = SummaryType.Sum;
    info1.Summaries.Add(summary);
                fs.ColumnSummaries.Add(info1);
 
                ColumnSummaryInfo info2 = new ColumnSummaryInfo();
                info2.ColumnKey = "POQuantity";
    Summary summary = new Summary();
    summary.CustomSummaryName = "Total FG ";
    summary.SummaryType = SummaryType.Sum;
    info2.Summaries.Add(summary);
                fs.ColumnSummaries.Add(info2);
            }

However this will change the summary name only in the summary row. To change it in both places Summary Row and the Summary Selection window you may use something like:

        //Create SummarySetting
        SummarySetting ss = new SummarySetting();
        ss.CustomSummaryName = "Total FG";
        ss.SummaryType = SummaryType.Sum;

        //Create SummaryRowSetting
        SummaryRowSetting srs = new SummaryRowSetting(WebDataGridPicklistBatch, "FGQuantity");

        //Add SummarySetting to the SummaryRowSetting
        srs.SummarySettings.Add(ss);

        SummaryRow fs = WebDataGridPicklistBatch.Behaviors.CreateBehavior<SummaryRow>();
        fs.ColumnSettings.Add(srs);

        ColumnSummaryInfo info3 = new ColumnSummaryInfo();
        info3.ColumnKey = "FGQuantity";
        
        Summary summary = new Summary();
        summary.CustomSummaryName = "Total FG";
        summary.SummaryType = SummaryType.Sum;

        info3.Summaries.Add(summary);

        fs.ColumnSummaries.Add(info3);

Please let me know if these suggestions are helpful