eye adaption and its use

I don't know why but I am finding it extremely difficult to understand how to use eye adaption. I have tried making certain values positive negative, extremely high, extremely low, keeping values within normal, etc... but am having trouble figuring out how you are intended to use it.

Find a correct space (darker or brighter image). Disable and enable effect to see the changes. Play with the values to see how much image brightening/darkening you need (you should see more details popping out after enabling this effect).