Insert grid view data to already existing excel c#

My task is to add the Grid-view data to already formatted excel, I need to insert the fetching data from Grid-view to starting from second row after header, I don`t where I am doing wrong the code is inserting data after 2 row, please find my template excel, asp-dot-net code below.
Column1 Column2 Total1 =Sum(A2+B2) =Sum(A2+B2)  
Dotnet Code:
<%@ Page Title="Home Page" Language="C#" M ...