Change Grid size in css

hello, looking for some help, searching how to change theme grid size from 1296px to 1170px ; I'm using theme Quark, but can find any css file where to change px , I'm using XL grid , found some settting in _layouts.scss and _variables.scss where is size-xl and grid-xl I have changed to 1170px but it doesn't work, could somebody help me?