var numberformat = "#,##0.00_);(#,##0.00)";
 var dataCellStyleName = "TableNumber";
 var numStyle = package.Workbook.Styles.CreateNamedStyle(dataCellStyleName);
  numStyle.Style.Numberformat.Format = numberformat;

          //Add Value ...

var tbl = worksheet.Tables.Add(new ExcelAddressBase(fromRow: 1, fromCol: 1, toRow: list.Count + 1, toColumn: 3), "Data");
 tbl.ShowHeader = false;
 tbl.TableStyle = TableStyles.Light1;
 tbl.ShowTotal = true;

 tbl.Columns[2].DataCellStyleName = dataCellStyleName;
 tbl.Columns[2].TotalsRowFunction = RowFunctions.Sum;