This article helps you setup shipping costs for individual product and if you are selling a bulky / heavy / oversize item that needs to be shipped in a separate parcel, then you can enable the "Apply per box" setting.

A. Setup shipping to individual product(s) 

Refer to this KB article,

How do I add shipping charges to individual products? - Knowledgebase / Shipping and Taxes - ShopFactory Help Center (deskpro.com) 

- Enter Weight value for the heavy / bulky item in EditProduct dialog.

B. If your heavy/bulky item needs to be sent as a separate parcel, you can also use "Apply per box" setting in the shipping charges dialog

- Open your shop in ShopFactory

- Click Central dropdown -> Shipping Charges

- Click Next and then select the shipping method 

- Tick "Apply per box" and enter the maximum weight for that heavy / oversize item i.e. 20kg/lbs

***Repeat steps for all other shipping methods

- Click Finish button

- Save and preview your shop in external browser

- Place a test order by adding the bulky/heavy item to cart then add other products in cart to confirm the shipping charges are correct

- Publish your shop so the changes are uploaded online.