Shopping Cart in the Amazon App usually acts as a reminder for the products you are interested in. However, this does not mean that the product is reserved for you and no one else can buy it. You can only be guaranteed about the products reservation if you press “Place The Order” button.
However, a shopping cart allows you to modify your product in sense of its quantity before placing order.
1: Login to your Amazon Account.
2: Move to the Shopping Cart.
3: Click on the “quantity” item and press “update”.