LOreal creme casting hair colour
Not upto the mark

Hello

I have been using loreal creme casting hair color, shade darkest brown, for quite some time.

However, i wish to state that thought he package mentions 'lasts for 28 washings' my hair color will not last more than 2-3 washing if i wash it twice a week. I would like to know on what basis is the product manufacturer making such claims and if they are making such claims why is it not applicable in my case.