Throttle dual rates

Hi, I have a simple question about Expo&DR mixer on my T8SG:

for airplanes is ok to apply a Scale... but how do I apply Scale & offset for Throttle? because I need the bottom value to be always -100

can you use 3 point curve and set first point at -100 second two points where you need them?

I will do that, thanks. But it seems that in 1-to-1 an offset is missing, or maybe in adv curves.