In "To Kill a Mockingbird" what does Scout learn from Calpurnia's account of Zeebo's education?

Calpurnia
explains toandthat "There wasn't a school even when [Zeebo] was a boy," and mentions
that it was she that "made him learn, though."  She taught him how to read; that she
herself could read was unusual.  She said that she was taught by "Miss Maudie Atkinson's
aunt, old Miss Buford."  When Calpurnia taught Zeebo to read, he was older; he "had
half-grown children".  How she taught him was that she "made him get a page of the
Bible every day" and then used a book that their grandaddy Finch had given to her years
ago, and taught him to read using both of those sources.  So, through Calpurnia's tutelage,
Zeebo learned how to read.