Mask making adjustments to selection when initially applied.

You can check the box to tell LrC to reset everything for each newly made mask.

If that's not checked, then sequence matters: if you begin making a new mask (start brushing, place the position of the gradient filter, whatever) and then move adjustment sliders around, those changed adjustment sliders are specific to this new mask only. 

But if you select to make a new mask and then move sliders around before you have yet started any brushing (say), then these changed sliders become the new default adjustments not only for this current mask, but also for future ones, until you say different. So this can be used to your advantage, maybe, if you want to brush some sort of consistent adjustment onto a succession of different pictures.

Unless usage of any non-zero default is being prevented, by a checkmark in 'Reset Sliders Automatically'.