It means that as we have seven days in a week. spend 6 days of it learning whatever thing you wish to learn, say English. And spend at least 1 hour learning it in each day. Thus, 6 x 1 = 6. You have 6 hours of study each week. At least 24 hours a month. A lot per year. Of course, it doesn't limit you to one hour only, you could always exceed as you wish to.
The main principle here is to study everyday, even for at least an hour, and you would absorb greater of what you are learning for sure. Take time to rest too on the seventh day.
I hope this helps!