You're getting different ways of saying the same thing confused. The powerbox wants a good range for the "one end, other end" movement. They're calling one end "0%" and the other end, "100%". For Futaba, "0%" is the center of the channel's movement, so one end is 100% in that direction and the other end is 100% in that direction.

Just use the 100% endpoints (or more) and you'll be OK.