Power Supplies Total Load
Based upon your commentary and the photos the 4 power supplies are connected in parallel to the mains supply. This has been achieved by looping the main power connections to each psu in turn. If the psus individually draw 6.8 A (per label) then the total draw on the mains is 4 x 6.8 = 27.2 A
In theory the looped mains cables are servicing less current e.g. the last cable is only providing 6.8 A to it's psu. You could use a cable with a lower rating but it would cost more to manufacture and would be inherently less tolerant to failure. It makes sense to just using the same cabling spec throughout.
Per the spec on the psus your total draw could be 27.2 A but what it actually is would be dependent on the load e.g. there could be design margin in the psu choice and clearly the psus are a third-party part which met the design criteria. So the Blue 20 A connect might be underspec with regard to the maximum psu load but still ok for the application in question. I would have expected it to be rated at 30 A for safety margin but without more specific design detail one wouldn't know.