Because it was felt that a school day would last at least eight hours, and you wanted the child to have the ability to use the laptop for at least one full day without having to recharge it.
하루의 학교 일정을 8시간으로 생각했을 때, 아동이 최소한 하루 동안은 다시 충전할 필요 없이 노트북을 사용할 수 있게 하기 위해서였죠.