USPS shipping help

I am trying figure out the best way to handle USPS shipping and I am easily confusing myself. We sell a product individually that has the dimensions of 6x6x7 and a weight of 4 pounds. The USPS plugin seems to be working properly with a single item, let's say the shipping rate is $8.30. But, often times a customer may buy 4 of those items and we will ship it in a box that is 19x13x6 weighing 16 pounds and USPS says it should be around 30 dollars. Now, if a customer adds 4 of the above items (6x6x7 4pounds) shouldn't the shipping rate be around $32.00? If I add 4 to my cart it shows shipping rate of $15.40.

I am not 100% certain that i have the shipping options configured properly.

Hello,

The USPS shipping plugin will only :
- Send to the USPS platform informations about your order (weight/dimensions/address/...)
- Display rates returned by the USPS platform

So if you approximately know which shipping price you want to charge for 4 products, the best solution will probably be to configure and use "manual" shipping methods, or adapt your USPS price using the "price" option.

I am trying to understand a little better about how this plugin works. If I add one product for example the shipping will cost 8.30 If I update the quantity of that product from 1 to 2 the shipping increases to 11.40. Adding one more in quantity (total of 3) the shipping increases to 13.95. Shouldn't the shipping be more given that the original price to ship one item was 8.30?

I do not see "group package" option. Where is that found?