I work in games where these values are extremely common and 'accuracy' wouldn't be very descriptive in a lot of circumstances: explosion radius falloff damage, water flow strength, positional/rotational lerps or easing, and more.

I wish I were commenting here with an answer, but I don't have one. "brightness01" is a common naming convention for values of this type in computer graphics programming, but niche enough that it got raised in review comments by another gameplay programmer.