EDIT: Q - why 0-5 and not 0-7 triggers? I'm worried I spoke too soon about following plans...
A 0-7-triggered plate would be triggered all the time and therefore useless.
I used 6-7 triggered plates on the adders. This meant that when water pathing was closed off to a certain plate by a change in the state of the adder, it would only have to drain down to 5 before shutting off. This doesn't normally cause a delay when water pathing
opens to a given plate, because the water coming in is under pressure and fills up to 7s very quickly.
If I'd used, say, a 1-7 plate, the plates wouldn't clear until they drained
and evaporated completely. No good.
A (2-4)-7 might also be alternately triggered and released during the draining process when I've shut off the water into the system and am allowing it to drain out of everything (no longer under pressure), which is also undesirable.
I said 0-5 triggers for the display controller with the idea of using bridges for the display segments. When a plate becomes triggered it sends an "open" signal and when it becomes untriggered it sends a "close" signal; a 0-5 trigger plate will be triggered in air, but when submerged in 7/7 water would untrigger, and send a "close" signal to the retracting bridge which would then extend. When blocked, and drained to 5 or lower, the plate would trigger again and retract the bridge.
The inverted case of the unusable 1-7 plate I used in contrast to the 6-7 plate would be a 0-0 plate.
If you're using gear assemblies, it doesn't actually matter whether you use a 0-5 or 6-7 plate, because gear assemblies just toggle their state when they receive either signal. You have to link them to an initialization lever to make sure they start in the state you want them in.
You could even use a 0-5 and a 6-7 plate together in each segment, if your display design called for using a 6-7 plate to open a hatch to pour water into a channel when a segment is on, and then having a 0-5 plate linked to a hatch that would let it drain back out.
If you wanted to
pump water into a channel when a segment's on and pump it out when it's empty, you would use either sort of plate, and link it to the gears that transfer power to both pumps, but link the gear to the flood pump to some throwaway lever and then pull that lever to disengage it until the plate's submerged and changes state.