I didn't study so many years ago

I am not from the same country as Duke university. Universities in other places work quite different from that. We have employees from many other countries and I'm quite satisfied by their work and understanding, even the youngest ones.

send letters explaining why the letters actually mean.

Not sure what you mean; if you refer to explaining why their grade is not top level... What kinds of jobs are people getting over there? I'd laugh at someone asking my university grade to employ me. No, I have never asked what the grade of a candidate was. Rarely look at which university they studied, I might at most be interested in which countries they studied and worked and what their thesis was about.