Volume Levels 
Volume 10: If your goal is toning, making your hair darker, or blending gray without significant lift.
Volume 20: For standard gray coverage or lifting your current color by one to two shades.
Volume 30: When you need to lift your hair by two to three levels or want to achieve a lighter result.
Volume 40: Maximum hair lightening and bleaching -lifting hair up to 4-5 levels. It is used for dramatic color changes, creating high-lift blondes, and for lightening dark hair.
Volume 50: used for strong, rapid hair lightening to lift hair color by approximately five levels.