They've stuck fairly obvious 50 = Window 51 = Aisle stickers all over them now, and the placement makes it obvious. Was a bit hard to decipher before, thanks to the seat hand-hold stickers not liking to stick and ending up in the vacuums.
From aaages of experience of these blasted things:
Available = You can sit here, but expect someone with a badly printed ticket to rock up and claim you're in their seat because they have mistaken 8 for 0.
Reserved = Either this is a reservation for the entire journey or just part of it (and you've got on at the station the reservation started at, or one after)
Available Until.... = The train hasn't arrived at wherever the display says. As soon as it does arrive (linked to the PIS deciding you've arrived) the displays update simply to "Reserved"
One stupid oversight on these boards is that they have more characters than the system can support, so text gets truncated despite there being plenty of space left on the LCD. I really should count exactly how many letters they can handle, so I can figure out something the bookers wont balk at but ends up on the trains themselves with an entirely different message. Donalds Big Assistance team meeting perhaps