Level 5 corresponds to a light brown on the universal colorimetry scale (1 = black, 10 = lightest blonde). It measures the lightness or darkness of hair, independent of the reflect.
The ash (.1) reflect adds a cool, gray-blue undertone that neutralizes warmth. It is the most requested reflect for counteracting orange or yellow tones. Ideal for those who prefer a cool, sophisticated result without visible warmth.
Each brand codes level and reflect differently. The table above shows how the major professional brands name this same shade: level 5, ash reflect.