I think I would make the same conclusion as you made.In our
company manual it says that our engineering department calculates the ACN but that a certain runway overload is allowed.
How much this is I have no idea. I assume this is done after making contact with the aerodrome in question. I will try to get back to you on Monday/Tuesday after I have had contact with the
pro's in my company.And by the way, we also use Aerad.
Rgds.