Hi, I'm a Canadian Citizen living in the UK and I was also thinking of applying to UofT however, have gone off the idea. But I have done quite a bit of research in the process so I think I can help. I think that they will most likely consider the further maths and maths as two subjects but if you want to know for sure you can e-mail their support team and they normally reply quite quickly. Either way because the UK curriculum is somewhat harder and more accelerated than the Canadian curriculum they actually only require you to have AS levels and by completing your A-levels you may actually be eligible for first year credit meaning you can take less classes as they will be covering things which were covered in your A-level courses. Because you took AS chemistry this could act as your third subject provided they do not consider further maths and maths separately.