In reply to your message of a week ago...
I don't know exactly how that grading works, but 87% doesn't look bad at all. What is the minimum requirement, 60%? Don't worry, you at least have your direction clearly. A friend of mine was indecisive between Greek/Latin, Biology, Medics as well as a bunch of other stuff, and that very close to the deadline and she managed to make a good choice in the end as well.
For myself, I was thinking about going for Chemistry like three years before I had to choose. I looked at some other things as well, but they didn't seem as appealing, so it was an easy choice for me.