How to show the total summary value in DateTime format using custom aggregate in WinForms DataGrid (SfDataGrid)?

public Form2()
{
    InitializeComponent();
    this.sfDataGrid.DataSource = this.CreateTable();
    this.sfDataGrid.TableSummaryRows.Add(new GridTableSummaryRow()
    {
        Name = "tableSumamryTrue",
        ShowSummaryInRow = false,
        Title = "Total :  {TotalTime}",
        SummaryColumns = new System.Collections.ObjectModel.ObservableCollection<Syncfusion.Data.ISummaryColumn>()
        {
            new GridSummaryColumn()
            {
                Name = "TotalTime",
               CustomAggregate=new CustomSummary(),
                SummaryType=SummaryType.Custom,
                Format="Total time : {TotalHours}",
                MappingName="Time in minutes"
            },
        }
    });
}
 
public class CustomSummary : ISummaryAggregate
{
    public CustomSummary()
    { }
    private string totalHours;
    public string TotalHours { get { return totalHours; } set { totalHours = value; } }
    public Action<IEnumerable, string, PropertyDescriptor> CalculateAggregateFunc()
    {
        return (items, property, pd) =>
        {
            var enumerableItems = items as IEnumerable<SalesByYear>;
 
            //To check the summary format of the summary row.
            if (pd.Name == "TotalHours")
            {
                int total = 0;
                foreach (var item in items)
                {
                    DataRowView dr = item as DataRowView;
                    total += int.Parse(dr["Time in minutes"].ToString());
                }
 
                this.totalHours = total / 60 + " Hours : " + total % 60 + " minutes";
            }
        };
    }
}

Public Sub New()
 InitializeComponent()
 Me.sfDataGrid.DataSource = Me.CreateTable()
 Me.sfDataGrid.TableSummaryRows.Add(New GridTableSummaryRow() With {.Name = "tableSumamryTrue", .ShowSummaryInRow = False, .Title = "Total :  {TotalTime}", .SummaryColumns =      New System.Collections.ObjectModel.ObservableCollection(Of Syncfusion.Data.ISummaryColumn) (New Syncfusion.Data.ISummaryColumn() {New GridSummaryColumn() With {.Name = "TotalTime",     .CustomAggregate = New CustomSummary(), .SummaryType=SummaryType.Custom, .Format="Total time : {TotalHours}", .MappingName="Time in minutes"}})})
End Sub
 
Public Class CustomSummary
 Implements ISummaryAggregate
 Public Sub New()
 End Sub
    Private _totalHours As String
    Public Property TotalHours() As String
        Get
            Return _totalHours
        End Get
        Set(ByVal value As String)
            _totalHours = value
        End Set
    End Property
    Public Function CalculateAggregateFunc() As Action(Of IEnumerable, String, PropertyDescriptor) Implements ISummaryAggregate.CalculateAggregateFunc
        Return Sub(items, [property], pd)
                   If pd.Name = "TotalHours" Then
                       Dim total As Integer = 0
                       For Each item In items
                           Dim dr As DataRowView = TryCast(item, DataRowView)
                           total += Integer.Parse(dr("Time in minutes").ToString())
                       Next item
                       Me._totalHours = total \ 60 & " Hours : " & total Mod 60 & " minutes"
                   End If
               End Sub
    End Function
End Class