What the heck is that? You earlier posted a screen shot of your PSU's nameplate that listed 4 x 18A (+12v) rails that can support a capacity of 624W. But even 52A is sufficient. (624/12=52) The individual rails will always be rated for more than their total. That's why 4 x 18 = 72, but 72A x 12V equals 864. You always use the total wattage as the final specification if all rails are fully loaded... which in your case they won't be.