Failed to get sum of a specific row in php [duplicate]

Failed to get total of students in a specific class from mysqli

Am trying to get the sum of students in a specific class from table. I have a code that gets duplicated rows so I want to count those rows based on the Id passed forexample if the Id passed is for a student in class seven, I want to count all rows with seven and display the total number
Here is my code

<div class="bio">
                <span><b>Student's name: </b></span><span class="text-uppercase pl-3"><?php echo $row['student_name'] ?></span><br>
                <span><b>Position in class:</b></span> <span>47</span> out of <span>
                    <?php
                    $id = $_GET['id'];
                       $sql1 = "SELECT sigles, COUNT( sigles ) total_members FROM tbl_student GROUP BY sigles
                       HAVING total_members > 1;";
                       $res1 = mysqli_query($conn, $sql1);
                      //  echo $total_members;
                      $count = mysqli_num_rows($res1);
                      echo $count;
                      
                       

                    ?>
                </span> pupils <br>
                <span><b>Division:</b></span> <span>1</span>
            </div>

this is how my database looks
enter image description here

so am expecting the answer to be 4 since they are 4 sevens in the column