Not sure how it is in the UK, but here in the US, college rankings are a joke. Standards have been lowered significantly to ensure legacy and affirmative action admits are able to graduate. I’d go so far as to say an average 7-year-old kid could get straight As at any top American university. It’s all a giant joke right now.
Not implying that you’re dumb or anything, but I wouldn’t use college attendance as a proxy for your IQ. There is a significant amount of people at Harvard with unimpressive SAT scores (Which is an IQ test despite the naysayers).
Also, short-term memory recall is only one factor that makes up intelligence. The standard deviation of ability for recalling digits is also extremely small in that most people can do 6-8 digits, but a very small minority can do 9+. As most standardized tests have only a few variables one needs to consider to solve problems, I can see why someone with an average short-term memory but strong logic abilities can do well.
Have you tried taking a standardized or professional exam where each question bombards you with 5+ different variables to consider?
An example would be something like this taken from the American Actuarial Exam MFE sample question:
This question requires the exam-taker to hold 6 different variables in his head as well as simultaneously accessing his/her long-term memory to retrieve the knowledge of each variable to determine its significance in relation to the question as well as manipulating said variables to solve the problem.
This is, in my opinion, a very difficult question that most people at any top university in the world would be unable to solve even if s/he understood the material.
But yes, if I focus hard enough and when I’m at peak performance, I can read and recall 12 digits in 2 seconds. Or maybe I’m underestimating how long I look at it. Maybe it’s 3 seconds. In any case, I only stare at it for a few seconds.
I tested myself out of curiosity. People noticed I was able to memorize a new phone number pretty easily. US phone numbers have 10 digits. I didn’t think it was anything special until someone brought it up. 12 was my limit.
But again, unless you’re taking an exam with questions like the one above, having average short-term recall is not going to harm you. Very few things in life require me to tap out my short-term memory capacity. College work and exams play around with just 1 or 2 variables per question/assignment. White-collar work should be pretty simple, as you can work on just 1 or 2 assignments at the same time while holding the less urgent assignments at bay. Just write post-it notes to remind yourself of deadlines.
Unless you really want to become an Actuary in the US or Canada, I don’t see any problems you’ll run into. I’ve looked at other professional exams, and none are as rigorous as the US actuarial exams in terms of intellectual requirement. As long as you can manage 1-3 variables at the same time and regurgitate what you memorized, you can pass the other professional exams.