The death of Piggy has symbolic value. It shows the death of innocence of these boys, and the end of all rationality and civilized behavior.
The fallacy that can be identified and that can be discredited is the idea that African American people are inferior based on perceptions from an earlier time.
You can conclude that Rita enjoys being active and being around friends and family, so when she didn't have anything to do the rest of the summer she grew bored and lazy, which caused her to count and dwell on the fact that her friends weren't with her and how many days were left until they were.