In To Kill a Mockingbird, what did Atticus mean when he told Scout to delete the adjective and she would have the facts?
In chapter 7, Jem assures Scout that the older she gets, the better school becomes. Scout then elaborates on Jem's extravagant explanations of what he is learning in the sixth grade. She humorously describes Jem's "Egyptian Period," where he attempts to walk with a rigid posture like the Egyptians depicted in hieroglyphics. Jem tells Scout that Egyptians actually walked that way and were amazingly able to accomplish more than Americans ever did. He also tells her that the Ancient Egyptians invented toilet paper and perpetual embalming. When Scout consults her father about Jem's explanations, he tells her that if she were to delete the adjectives, she would have the facts. Atticus's comment is an idiom used to describe Jem's exaggerations and fantastical ideas. He is essentially telling Scout not to believe everything Jem says regarding the Egyptians, because he has a big imagination and a tendency to exaggerate.
In this line from Chapter 7, Atticus is not being literal. He is using figurative speech in an attempt to tell Scout to ignore the way that Jem is exaggerating his accounts of how school gets to be more interesting as you get older.
In this passage, Scout is unhappy because she thinks second grade is "grim." Jem does not really help -- he says that you don't learn anything that's any good until you get to sixth grade. At this point, Atticus tells Scout to delete the adjectives. What he means is that Jem is exaggerating -- school is not really pointless until sixth grade. But, at the same time, once you get past the exaggeration, there is a kernel of truth -- school does get more interesting, he says, as you get older.