Adding multiple totals/summary items to Gridview

Hi- 

We're trying to add multiple summary rows to a gridview, similar to the single ones being added here:

https://docs.telerik.com/devtools/winforms/controls/gridview/rows/summary-rows

Using that example, I added one total, but can't figure out how to add the others that I need:  The example code below just shows a total for TotalTax, but not the others.   Can you point me to any documentation that shows how to do this?   Thanks, Evan

            Me.RGV_RIA_Input_Summary.MasterTemplate.ShowTotals = True

            Dim summaryItem As New GridViewSummaryItem()
            Dim summaryItemState As New GridViewSummaryItem("State", "{0}", GridAggregateFunction.Last)
            Dim summaryItemTotalTax As New GridViewSummaryItem("TotalTax", "Total Tax = {0}", GridAggregateFunction.Sum)
            Dim summaryItemGrossSales As New GridViewSummaryItem("GrossSales", "Total Gross Sales = {0}", GridAggregateFunction.Sum)
            Dim summaryItemExemptionAmount As New GridViewSummaryItem("ExemptionAmount", "Total Exempt = {0}", GridAggregateFunction.Sum)
            Dim summaryItemTotalTaxableSales As New GridViewSummaryItem("TotalTaxableSales", "Total Taxable = {0}", GridAggregateFunction.Sum)
            Dim summaryRowItem2 As New GridViewSummaryRowItem(New GridViewSummaryItem() {summaryItemState, summaryItemTotalTax, summaryItemGrossSales, summaryItemExemptionAmount, summaryItemTotalTaxableSales})
            Me.RGV_RIA_Input_Summary.SummaryRowsTop.Add(summaryRowItem2)