How to change the default ship-to address when creating sales order in Fusion

I got information that in Fusion after choosing BU and customer when creating sales order, the default ship-to address would be the site firstly added with ship-to purpose.

When I had test, the firstly added site only has ship-to purpose, the secondly added site only has bill-to purpose and the thirdly added site has both ship-to and bill-to purpose. However the default ship-to address always showed the secondly added site(which only has bill-to purpose).

Thus I want to know what's the default rule of ship-to address when creating sales order?

And how we could change the default ship-to address? Thanks.