I have absolutely no personal experience at importing in Chile, but it sounds like a bit of a lottery from what you have written.
There surely must be some sort of set criteria that you can use to set your selling information by. I would contact the customs department directly and ask for some clarification, and ask for it in writing!
Now if it still remains as confusing as before, then it would be best to always assume the worst case scenario when creating a listing, and inform the customer of the potential of certain things being in play in regards to customs.
I know that's not the best way to try and sell a product, but if it is so volatile, then not covering these issues with the listing might give a customer a real fright when they get hit, and that will come straight back and bite you on the rear :(