Comment by Infain on Houkago no Idol ni wa Himitsu ga aru - Chapter 54

Us nerds, we have a different scale for grades:
100+ = perfect
100 = very good
99-90 = good
89-80 = almost fuc*** up/no lunch today
79-70 = trash/no food today, possible disownment
69 = funny but you're gonna get beaten up
<68 = generational embarrassment/disownment (you're fuc***)