Where does the ship weight number come from ?
The ship weight (ship wgt) number AZInsight shows comes from office Amazon's formula (also known as the Dimensional Weight Formula). You can learn more about formula here. Note although amazon says to roundup the shipping weight, AZInsight DOES NOT do this.
Here is official Amazon formula Dimensional Weight Formula
Length x Width x Height / 139
Example: 34″ x 23″ x 23″ = 17,986 cubic inches
17,986 divided by 139 = 129.39
So even if the package only weighs 30 lbs., you will be charged for 130 lbs. based on how large the box is.