Customer is shopping and adds an item to cart. The cart Icon displays an indicator that something has been added to cart & automagically updates with the amount of items in cart and the $$ amount of items in cart, without having to have a page refresh.
Customer is shopping and adds an item to cart. The cart icon displays an indicator that something has been added to cart BUT the item & $$ amount is still 0.
If you navigate to another page it updates, but not until a page refresh is forced to happen.