FBM shipping fees for shipping from UK to EU

We are getting a little confused about shipping rates for FBM orders. Please could we have some clarification?

We are a UK company that will be shipping to the UK and to EU through FBM.

We have set up shipping rates for the UK side - and it has come to our attention that we probably need to set shipping rates for FR, DE, IT and ES as well.

However… the part we are getting confused about is this: in the shipping templates you can set domestic rates as well as international shipping rates for the EU countries.

So please can someone explain how this works if for example, a customer in Spain, is using Amazon.es to order from our amazon.es listing (when our stock is in the UK and will be dispatched from the UK to Spain). If the shipping template in Spain is empty it looks like the customer is getting free shipping. If we DO need to set up a shipping template in Spain, do we need to fill out shipping rates for domestic OR international settings in this specific example? How does Amazon know which shipping fee to use (when we intend to dispatch stock from UK to EU)

It was my understanding that the shipping rates set on amazon.es would be for a Spanish customer ordering on amazon.es and the company/stock they are ordering is within Spain itself also. And the international setting on amazon.es would be for someone outside of Spain, using amazon.es to order an item. Does that make sense?

Please could this be clarified? Thank you very much.