Water treatment question

Are recommended ion concentrations (ie Bru’n Water) for the post-boil or pre-boil volume?

I typically boil off 15%.

Given that everyone has their own system and boil-off will vary, I assume it would be more accurate to recommend ion concentrations for post-boil, but in my efforts to understand the water additions, it seems to be more concerned with pre-boil.

They are pre boil.

Yeah, there are so many variables that it would be impossible to estimate what the post boil ion concentrations would be. They are pre-boil concentrations.