Very widely discussed over the years here if you do some searches and want to read more. From my measurements with those plug-in meters, LED pins idle under 0.5A and ask for about 1-2A during play, occasionally some will ask for a bit more (like JJPotC, I think that spiked at like 2.5-3). I personally go 8 pins per 20A but they're rarely all on at the same time so it doesn't really matter.