router-alert feature in DDoS prevention - MX series

Question

I'm reading DDoS Prevention in MX series - 2nd. As mentioned in book "you can also configure whether an individual policer type should bypass that group’s aggregate policer"

=> I don't understand that mention. Please healp me! is mean the router-alert policer will match and the aggregate policer will be bypass although it has config bw limit 10k?

protocols {
    ip-options {
        aggregate {
            bandwidth 10000;
            burst 500;
        }
        unclassified {
            priority medium;
        }
        router-alert {
            bandwidth 5000;
            recover-time 150;
            priority high;
        }
    }
}

Answer 1

You could e.g. limit bandwidth from the Internet in general, but override the limit for your company's cloud server.

An individual policer has higher priority than a general policer, so the former can 'bypass' a rule that would be in place otherwise.