Below are the differences between subtotal & total:
This is the total price for each product in your order or the total price found for a selected delivery window in your order. If you also have a discount applied to a product, then you will find the updated discount price total for that particular item or delivery window in your order.
This is the overall adjusted total calculated price for all of the products in your order. If you have applied additional discount and/or surcharge to your order, then you will find the updated total price to include the discount and/or surcharge for your items.
From the working order page view:
From the order review view: