About Larger packages Setting

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the Larger packages setting to the result is suit to mine ,
how does it work ?out off my thinking !
2 x 4.58kg=9.16kg
is lower than 1 x 9.50kg,but the shipping price is higher .


Larger packages
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Total Items: 10 Weight: 9kg Amount: $2,990.00

Shipping quotes are based on the address information you selected:
Hong Kong
Available Shipping Methods Rates
DHL Rates (Shipping to Hong Kong (2 x 4.58kg)) $130.25

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Package Tare Small to Medium
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Total Items: 10 Weight: 9kg Amount: $2,990.00

Shipping quotes are based on the address information you selected:
Hong Kong
Available Shipping Methods Rates
DHL Rates (Shipping to Hong Kong (1 x 9.50kg)) $112.64

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I find out how does it work ,if it need 2 packs for the goods ,
it will calculate like below .

1 pack_shipping_cost * pack_num

so the price is different to 1 pack's shipping cost .