Can you explain how shipping is calculated when the "per product item"

Can you explain how shipping is calculated when the "per product item" is setup correctly. I am using this feature and the shipping fee came out different than expected

Hi, thank you for contacting JotForm support.

Could you please tell us the form URL in question so we can check? Also, can you please tell us what and how much you would charge the buyer for the shipping so we can properly assist you?

Please note that you'll see additional options after enabling the shipping option. You can add an additional shipping charge in these options:

1. PER PRODUCT ITEM - For PER PRODUCT ITEM, you have to specify the cost of shipping each item.
2. PER TRANSACTION (Flat Rate) - For PER TRANSACTION (Flat Rate), your buyers will be charged for the shipping cost you specify regardless of what item they choose or how many they buy from your payment field.
3. PayPal Payment Integration- For forms with PayPal Integration, you can specify a weight value for each product. These values will be used if you have a weight-based shipping method configured under your Paypal account.

We look forward to your response.