checkbox always checked and do something

I have input type checkbox in html looks like this:

<?php
            $result = $db->get_results("SELECT * FROM site_gst where description='YES'");
            foreach ((Array) $result as $r){ ?>
            <input type="checkbox" name="line_description2[]" id="line_description2_1"  
            required value="<?php echo $r->description ?>|<?php echo $r->is_gst_applicable ?>" 
            checked><?php echo $r->description;?>
                <?php } ?>

In the form, the checkbox is always checked. If the user uncheck, it will perform calculation. If the checkbox remain checked, it also perform a calculation. Here is my JQuery that i get so far :

jQuery(document).on("change", "[id^='line_description2_']", function() {
    var line_desc_id = jQuery(this).attr("id");
    var split_id = line_desc_id.split("_"); // id has value line_description_x. so value of x is at index 2
    var line_desc_val = jQuery(this).val();
    var split_val = line_desc_val.split("|");



    if ($(this).is(':checked')) {
    jQuery("#line_gstflag_"+split_id[2]).val("1");

                                }
    else  {
    jQuery("#line_gstflag_"+split_id[2]).val("0");
          }

If Im using this JQuery, the problem is, the user need to uncheck 1st, then checked again the checkbox to perform a calculation which is do this statement jQuery("#line_gstflag_"+split_id[2]).val("1"); and then if the user want to perform the other calculation, it need to uncheck back. I want it perform its calculation which is do this statement jQuery("#line_gstflag_"+split_id[2]).val("1"); without uncheck, then checked back. The user need to unchecked 1st then checked back to perform this statement. thats the problem. Thanks In Advance.