Can anyone actually parse Aeromexico's excess baggage policy?

Trying to determine how much I'd pay for 2 bags for a roundtrip YVR -> SCL flight, connecting in Mexico City.

My online itinerary just says "no info" for each bag, and gives this link which at least for me just loads as a blank page on both Firefox and Chrome.

On the other hand, this page seems to be what I want. At the very top, in the "Baggage Allowance" section, you can select your departure & arrival countries, and the table below updates. For example, when departing Canada and arriving in South America (except Brazil) in economy it looks like I get one checked bag free (note that this conflicts with what seatguru says which is 2 bags, but maybe they are just out of date).

OK, so how much for the second bag? Click "Excess Baggage Fees" in the header (I can't seem to link to this directly). You get a confusing table, the first few rows which look like this:

First, immediately above, it says Select your route to consult our baggage fee schedule. That kind of seems to imply that maybe the stuff I selected at the top regarding my route affects this table, but it doesn't: it's just an unchanging table.

I'm going to assume I'm interesting in the "Per piece at the airport" column, but I'll still note that even the other columns are confusing: there is "Per Volume" column, but no units? Is it just a fixed fee for any bag which exceeds the linear dimension rules or what?

OK, so how do I look up the right row? The heading says Origin/Destination. So which is it? Why is there a slash? I'm flying from Canada to South America, do I use my origin or my destination?

Let's assume I use the origin, and so the US & Canada row. It says First Piece = 25 USD - but from the "Baggage Allowance" section I'm pretty sure my first piece is free. What gives? Is it the first excess piece then (i.e., my second piece?). That interpretation doesn't make sense though given that the other rows don't have any "first piece" entry at all, so I think it really is the first piece (but perhaps the baggage allowance overrides it).

Ultimately, I'm guessing that my second piece of luggage will cost 55 USD, but any help in parsing this is still appreciated.