Platinum Blond 10.0 is formulated to create a very light, cool blonde tone. The exact final shade you achieve is not guaranteed and depends almost entirely on your starting hair color, which acts as the base for the new pigment. According to the product description, if you have a medium brown natural color, it is very unlikely you will reach the platinum blonde pictured on the box in a single application. The pigments are designed for even coverage and longevity, but they work by depositing color onto and lightening your existing hair; they are not a high-lift bleach.
For a significant color change from a darker base (like brown) to a very light blonde, a two-step process is standard practice. First, the hair must be pre-lightened (bleached) to a pale yellow or orange base, close to a level 9 or 10. Only then can a toner or direct dye like this Platinum Blond shade be applied to achieve the desired cool, ashy, or platinum result without brassy undertones. Applying this product directly to untreated medium or dark brown hair will likely result in a warmer, golden, or reddish blonde, not a platinum tone. For the most predictable outcome, consulting a professional colorist for an assessment is strongly advised, especially if your hair has been previously colored or is resistant.