Views:

The CM1-AES50 has two AES50 ports built into it.  These are labelled as Primary and Secondary.  The maximum channel count is 48 channels bidirectionally, whether at 96 or 48 KHz

At 96KHz both ports carry 24 channels each bidirectionally as this is the maximum channel count for AES50 at 96KHz.  The port labelled Primary is channels 1 - 24 and the port labelled secondary is channels 25 - 48.

At 48KHz, there is only one port active at any time.  The other port acts as a cable redundancy.  The Primary carries all 48 channels bidirectionally with the Secondary as the redundant.