The next tab on the Shipping Agent Service Card is the Packaging tab. The defaults in this list are based on the Shipping Agent app you installed.
You are then expected to go into each packaging code and edit the card which holds information around weights and package dimensions. To this click on the code of the package code that you want to edit, which open the card related to it.
The details you populate on this packaging card will pass through to the Shipping Agent when you register the Posted Sales Shipment with them (this will be detailed further on it the document).
There are limitations which each Shipping Agent has around what values you can populate the fields with so please check with them before you populate it with a value which they can’t handle.
NB: It may be that you prefer to remove the packaging types they won’t be using.