It seems that any discounts set using the scripts editor isn't reflected in the carrier shipping call. Since the scripts editor applies discounts to each line item there shouldn't be any reason the price isn't reflected, after all if you set an item on 'sale' this new value is in the carrier shipping call.
What this means is, customers may pay extra shipping as customs tax/insurance will be higher due to the higher order total reported.
Any chance the carrier shipping API can reflect the discounted numbers?
Second this, but this also plays into the whole big issue that Shopify does not apply line item discounts for coupons either which creates the same problem.
It is a shame there is a disconnect between Carrier Service API Payloads and the Plus Script Edit results, as well as plain jane discounts.
Would be Super Swell if some Friday Hackathon addressed these long-ish standing issues! Shipping depends on the right numbers to make the right rates!