Ripple performance
Ripple is a by product of converting AC to DC, and it's characterised by tiny voltage fluctuations that need to be suppressed in order to deliver clean power to your components.
As usual, there are standards for this kind of thing, with the ATX spec stating that ripple shouldn't exceed 120mV evaluated as a peak-to-peak value.
Gigabyte is well within specification but not as good as the other two. Is 27.3mV anything to worry about? Not at all.