What they are trying to say (but might be legally prevented from saying) is that it was probably replaced with a third party battery at some point as no sanctioned battery should have any extra markings on it. Said third party battery (which might well even be one of theirs that technically failed testing, was made during a ghost shift, was stolen somewhere in China, was recovered from a dead phone....) could be dangerous, but in all likelihood is not.
You will likely have to go find one of those phone repair places and get them to source a new battery (I don't know about Canada but they did try to prevent shipping to the US a while back so that might be easier said than done). Bonus is that it will probably be cheaper than getting Apple to do it.
Or if you like you can do it yourself. It is usually not so hard, though I have not kept up with the latest models.