If you could not care less then you most likely don't take selfies in the first place. Therefore the phone would be of absolutely no interest to you.
However, if you could care less then you do take selfies, but not care enough to buy a phone specifically for that purpose.
The latter scenario was the point the author was making in his statement. Logic was used properly in that case.
However, if you could care less then you do take selfies, but not care enough to buy a phone specifically for that purpose.
The latter scenario was the point the author was making in his statement. Logic was used properly in that case.