What does it mean when the hair is under-lightened? it is not tened to the esired level it is not healthy enough to lighten it is too light for the toner square the toner has not been on the hair long

When hair is under-lightened, it means that the hair is not lightened to the desired level. This can happen when the hair is not lightened enough to achieve the desired shade or when the toner has not been applied long enough to achieve the desired result. It is important to note that under-lightened hair is not necessarily unhealthy, but it may require additional lightening treatments to achieve the desired result.