I think you are thinking of the phrase  the other way around , which does essentially mean the opposite, but in a specific way. The specific nature of the other way around is that it means that doing what you say in the opposite direction is correct, not necessarily the exact opposite.
Once kittens reach 4 weeks of age, their mother usually begins to wean them off milk and onto solid foods. Because the weaning process can take up to six weeks, purchase a small amount of kitten milk replacement formula and mix it into your kitten's food during his first two weeks with you.
How to Feed a Newborn Kitten. Ideally, kittens should stay near and nurse from their mother cat for up to eight weeks prior to being separated and/or adopted. In the case of a rescue, death of the natural mother, or when circumstances cause cat mothers to reject one or more of her litter, human intervention is necessary.