The numismatic definition of "good" as "well, it's pretty bad, actually" does trip up many newcomers to the hobby.
The reason why we use "good" this way is historic. Way back when coin collecting was beginning, during the Renaissance, "Good" actually did mean "pretty good". The original grade levels were Poor, Fair, Good and Fine. And for ancient Greek and Roman coins (which was all anyone collected back then) found by accident in the age before metal detectors, these were all the grading levels they needed. As coin collecting progressed and as coin production technology improved, grades ever higher than "Fine" had to be invented, as well as interstitial grades in between the original four.
Gradeflation has happened since, as well. Today's "Very Fine" coin would have been called "Good" 300 years ago.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis