Does UBC calculate 'grade average' from just 12th grade?

On the website, it sounded like they use your semester one 12th grade grades, and in some circumstances your 11th grade semester two grades. Is this correct for international applicants?

I’m really nervous, because if it is I have a 95% or a 98% (first is the actual average of my final class percentages, second is my GPA converted) in the 4 core classes, but if they go back further (to sophomore/freshman year) I’m not nearly as competitive. Junior year is the same. It’s not HORRIBLE, but it would be like a high 80 something. I never failed anything, and I’m taking all APs in the core classes they care about, so really I’m just worried about how far they’ll look at my actual grades.