get value from cart total or subtotal

Hi,
I use the module for calculating delivery by local carrier,but the module do not calculate shipping costs to the total.
In the “wp-content / plugins / woocommerce / templates / order / order-details.php” I added the following code to take the amount of shipping and subtotal:

‘<? php $ a = array (
get_post_meta ($ order_id, ‘Order_subtotal’, true),
get_post_meta ($ order_id, ‘Econt_Customer_Shipping_Cost’, true));
?>
<tr class = “total-cost”>
<th> <? php _e ( ‘Total:’, ‘woocommerce’); ?> </ Th>
<Td> <? php echo array_sum ($ a); ?> <? php echo get_woocommerce_currency_symbol (); ?> </ td>
</ tr>’

As a result, I get only the value of “Econt_Customer_Shipping_Cost”, but not from “Order_subtotal” to get the total.
Please if someone can tell me what to use to get a subtotal.