score:1
MAD-GRU is a fifth-freedom flight (a sixth-freedom flight is a form of fifth-freedom) that appears to fall under ii) B. and thus allows you a two piece allowance. The full route would be PEK-MAD-GRU
The wording is somewhat ambiguous, however I believe all flights to and from Brazil require that two pieces of check-in luggage are allowed. See: Why is the baggage allowance on flights to/from Brazil more generous?
A dummy booking for MAD-GRU on airchina.us and airchina.uk also shows 2 pieces:
Upvote:1
I believe you are only entitled to one piece of luggage.
ii) B is quite explicit about it: flight from a country other than China to Americas via China (defined as a sixth freedom flight), which is not the case here, you are flying from one country other than China to another country other than China (a fifth freedom flight).
Not sure if Air China do this, but many airlines make your actual allowance quite explicit on their βmanage my bookingβ pages (usually with an option to buy more), so I would recommend you check that.