ACMA is the first level of Aruba Mobility Certification. It demonstrates that you can install a single-controller network.
ACMP is the second level of Aruba Mobility Certification. It demonstrates that you can install a multi-controller network with more advanced firewall rules, redundancy, etc.
Some engineers that have worked with Aruba controllers for a long time may wish to skip ACMA and go straight to ACMP so that is why we don't require ACMA first.