Multi Box Shipments

[PTMShipping]

Hello, I'm looking for some ideas or answers for an issue we've been having. When people order X amount of our product, we have boxes that can fit up to 6 of this product per box. If they order more however, we have to use multiple boxes. When the customer pays for shipping, it does not take this into consideration when charging for shipping costs. We had a shipment to Australia where he had ordered 10 mirrors. We can only fit 6 per box max so we had to sent 2. Shopify charged him 500$ for shipping when we ended paying 1,110$ because we had to create 2 separate shipping labels, one for each box. So that means every shipment that requires more than one box to ship will result in a shipping cost loss on our end.  Is there anything in the settings to where this can be adjusted or does shipping cost have to manually be adjusted after an order is purchased? Anything will help, thanks!

[PTMShipping]

Yes, here you are. https://ptmwatersports.com/