Network security question.

If I have configured my network, Airport Extreme, sixth gen. with the following options:

Then why does my system respond to an unsolicted request?

Ping Reply: RECEIVED (FAILED) — Your system REPLIED to our Ping (ICMP Echo) requests, making it visible on the Internet. Most personal firewalls can be configured to block, drop, and ignore such ping requests in order to better hide systems from hackers.

This is highly recommended since "Ping" is among the oldest and most common methods used to locate systems prior to further exploitation.