How to add Button Text inside GridView to TextBox with line break on click using C# in ASP.Net

hi see below image:

as you see there is gridview that I define linkbutton when click on linkbutton it will add number from gridview into textbox that show with red arrow...

below is code of Linkbutton:

   protected void LBaddNumberG_Click(object sender, EventArgs e)
    {
        string numbers = string.Empty;
        GridViewRow row = (sender as LinkButton).NamingContainer as GridViewRow;
        numbers = (row.FindControl("Lblmobile") as Label).Text.Trim();
        TxtPhone.Text = numbers.Trim() + Environment.NewLine + TxtPhone.Text;
    }

now see below image:

here I add one number from gridview into text box as you see in above image I define label (blue arrow) that I want define that it display count of number that I add to textbox in above image it should display 1

and

now in above image I add 2 number to textbox I want in label that I  show with blue arrow it shows (2)...

how I can define that in label it shows count of number that I add to textbox?

best regards

neda