Based on what I've seen so far, the case should follow the last number, 21 (one - один) should be nom. sing. but when I was looking at the macbook pro on apple's web site, they describe the battery time in hours like this:
До 21 часа при воспроизведении фильмов из приложения Apple TV
До 14 часов работы в интернете по беспроводной сети
So my question is: shouldn't be "21 час" instead of "21 часа"? Or is there some other rule about numbers?