Exactly, they don't show how these people performed in a standardized exit test _after_ college, so there's no way to measure how well they did relative to each other in terms of education.
No, the article itself says the exit exam is for Secondary School, i.e. High School.
“India is atypical in that its college students have to take standardised exit exams. ”
The first figure has high school entrance exam as the x axis and college exit as the y.
I see lots of complaints in this thread that the article is inaccurate, but this is what it says.