I am almost 100% sure she is inflating her grades. Either Ruby is the greatest conwoman alive and she's been putting on a carefully curated façade for the past 5 years, pretending to be a gigantic idiot who can't even put two words together in a sentence in her own native language, or she's lying to make herself look like a genius to her young, impressionable audience.
I've also thought that maybe she counts on the fact that a large part of her audience is not British and doesn't know that an 80 is such a phenomenal grade. In my country a 24/30 is nothing to write home about. A lot of people would actually turn it down (in Italy you can choose to turn down grades and try the exam again in the next exam session if you're not happy with them, even if you got a passing grade).
I've also thought that maybe she counts on the fact that a large part of her audience is not British and doesn't know that an 80 is such a phenomenal grade. In my country a 24/30 is nothing to write home about. A lot of people would actually turn it down (in Italy you can choose to turn down grades and try the exam again in the next exam session if you're not happy with them, even if you got a passing grade).