First of all, never trust a box of hair color. The way hair color works is there is a pigment, which is the color, that is then mixed with a developer (peroxide) and the strength of the developer determines how the color will either lift or deposit as well as how it will leave the integrity of the hair.
As a professional colorist, I never use developer higher than 20 volume which is pretty gentle. In boxes, they package the color with 40 volume, which is a very strong and potent developer. Because this product is so strong, it can be very damaging to the hair and also extremely difficult to remove or adjust.
It’s challenging for hair colorists to have a client come in and say that they just used box color and would now like you to correct it. Save yourself time, money & nightmare hair, and just see a stylist instead.