What is the problem?
The "Little Women" exercise in the finding things episode uses grep -o but never explains what grep -o does or why it is used here. There isn't any hint in the exercise to lookup this option in the manpage/help either.
Without using -o a slightly different answer comes up because some lines contain a name twice and using -o counts all instances, not using it will count them all as one. A possible workaround could be to ask for the number of lines containing each person, not the number of times their name appears in the text.
Location of problem (optional)
https://swcarpentry.github.io/shell-novice/07-find.html