Miscalculation Of Shippinf Fee

Hi Guys.
Using the free version at the moment but will definately upgrade in the near future.

We will be selling darts, ive set up a few test products, one being a set of dart flights which are plastic, lets say 1 inch round and under 1mm thick and weighing 20gms. I do a test purchase and it shows $8.94 to post them? Ive double checked and triple checked settings and dimensions, it appears $8.94 is the cheapes and its going by parcel post when in fact numerous sets would easily go in a padded bag or envelope.

How do i resolve this issue? Please use basic terms as my skill level is very low.

Thanks.

https://www.ads-software.com/plugins/australian-post-woocommerce-extension/