Hi James,
I assume you used the wizard to generate the service call. The last step of this wizard prompts you to decide if you want to assign the values of the return parameters as context nodes of the controller or as parameters of the ABAP Service call response.
If you plan to use these fields in screens or in other components, then choose to have them as context nodes. You can then map this context to other screens/components. If the context values change, it is reflected whereever the context is shared and can be achieved without explicitly writing code to perform the transfer.
If you choose to have them as parameters, which I think is the default option. Then the values will only be available as parameters of your source call, for you to work with.
It sounds like you are getting to grips with context mapping, so I'll see if I can find a link to some decent documentation if your course content is not working out. Let me know and I'll see what I can find.
Cheers,
Katan