Hello from Amazon Selling Partner Support,
 
We understand that you are facing an issue with the shipping template setup where the shipping charge is applied only once per order, even if the customer orders multiple pieces. We acknowledge that you want the shipping charge to be applied for each piece ordered in the same order.
 
After carefully reviewing your shipping settings, we are able to confirm that your shipping fee are set to "per order" fee and "per LB/pound" fee instead of being set to "per item" fee. 

In order for you to configure this setting, you'll have to set the setting to "per item". Please follow the steps below:

1. Go to "Shipping Settings"
2. Under the "Standard Shipping", you will need to change the shipping fees per region according to your preference by clicking the drop-down under the shipping fee boxes.

Note that "per pound" and "per item" are the only options you can choose from.

And to extend our knowledge, you may want to visit the help page below in order for you to know more about the shipping rates and what is more likely helpful for your products.

Set your shipping rates
https://sellercentral.amazon.com/help/hub/reference/G200501930