Counter count to 10, end then 10,10,10,10,...at 1 to 9 is ev

Question

Counter count to 10, end then 10,10,10,10,...at 1 to 9 is everithing is ok...

 

What is wrong

SqlDataReader rdr;
                            SqlCommand cmd = new SqlCommand();


                            cmd.CommandText = "select max(brojprijavnice2) from dbo.prijava_radnika ";
                            cmd.Connection = con;
                            con.Open();
                            rdr = cmd.ExecuteReader();
                            int max = 0;
                            while (rdr.Read())
                            {
                                max = Convert.ToInt32(rdr[0].ToString());
                                Console.WriteLine(max);

                            }
                            con.Close();


                            String updateStaff = "UPDATE [dbo].[prijava_radnika] SET [vrijemeodjave] = @vrijemeodjave, brojprijavnice2 = '" + (max+1) + "', [status] = 'odjavljen' WHERE radnik = '" + readerresultTextbox.Text + "' and [status] = 'prijavljen'";