"In N+N AC Redundant power mode, a minimum of two power supplies is required. N power supplies provide power and N provide redundancy, where N can equal 1, 2, or 3.
The Onboard Administrator reserves sufficient power so that any number of power supplies from 1 to 3 can fail, and the enclosure will continue to operate at full performance on the remaining line feed. When correctly wired with redundant AC line feeds, the AC Redundant mode ensures that an AC line feed failure will not cause the enclosure to power off.
The AC Redundant mode provides full redundancy and is the configuration requested by large enterprise customers because it ensures full performance with one power line feed."
So, if you were fully populated with PSUs for example, then 1,2,3 would go to A, and 4,5,6, would go to B