Each channel can handle 6A on it’s own, but you can’t run all 4 channels at 6A because then the total would be 24A.

The power input terminals are the bottleneck, because all power for all channels flows through those two terminals.  UL rates those terminals for 16A.  The manufacturer rates them for 20A, and we’ve tested them at 20A with no problems.

This means you can run all 4 channels at 5A, a total of 20A.

Or you can run any combination of loads that doesn’t exceed 20A, as long as no single dimmer output is handling more than 6A.