I add up all the shipping costs on the picking slip you put with my order and it doesnt add up to the total shipping cost?

Shipping for express orders is a formula which is a fixed cost to your postcode plus a cost per gram. Each line on the picking slip only shows the cost per gram and does not include the fixed cost. If you add up all the costs on each line of your picking slip this will be the total variable cost of your parcel but does not include the fixed component.