SGU student here. Your numbers are pretty much on par. August entering students have about 1,000 students entering, and january has about 600, so there's really like 1600 entering each year and then yeah, about 800-900 end up matching. There's one match/graduation a year, so they lump the jan and august class together as one, so you can combine them as 1600 a year start. Rumors are that this august class will have 1100 students entering, so numbers keep going up and up, it's insane.
I know from my starting class last august, about 200 have dropped out/had to repeat already, so they weed people out pretty quickly in basic sciences, and then of course those can't pass step.
They do play with the numbers a lot here. I must admit that they do accept a good amount of students that are just not ready for med school and cannot handle it, I have met many of these people and they have dropped out already. They also take in a good amount of local Grenadian and trinidad students and a good amount of them cannot make it through to match because of either the rigor of studies here, or getting visas for the US. Then, in the 860 that end up matching, they also factor in those who had to re-apply to match a second or third year.
Therefore, i'd say it is closer to 50% of those that start end up matching the first time around. I've noticed how naive students here from Canada are about the difficulty of getting a residency back in Canada. It is extremely difficult for Canadians.
Now, even though around 50% make it through, you have to think who the people are that aren't making it through. Like I said, it's mostly caribbean students, or other students that were accepted to SGU but shouldn't of been.. they just can't handle it and have no place here, and even if they barely scrape by grade wise, they can't pass step 1.
To the OP- I suggest re-taking the MCAT and look into DO if you still can't get into Canadian/US schools. Just know that if you are Canadian it is extremely difficult to match in Canada as an IMG from SGU or anywhere else. With a 492 you should get into SGU (if your gpa is truly a 3.9), as long as you do well on the interview. It's a risk coming here, so exhaust all your other options first and be very very educated into those risks and what you need to do to do well here. It's one thing to say "I am very determined and will study hard here and do well." Most students say that and they just don't realize what it takes, emotionally and physically to do well here in the carib. By well, I mean around 85% grades or higher, which is what you need to stay competitive to match and correlates with a good step score. Just be educated, that is all.