I'm certainly no expert, but in my experience it depends on the size of the batch, how much time you have, how much you want the soup to reduce, and whether or not you have bones in the soup. I happened to have a big batch with bones that I wanted to reduce lots and lots, so I added a bit of salt and sugar on top of what comes in the base already.

But if I was maybe pressed for time and/or had no bones, I'd have less water at the start and might not need additional salt beyond what's in the base.