I was reading a Design Patterns in Java programming book and came across a new phrase. I'm wondering what does off the top mean in this particular context.
Excerpt from the book:
Somehow, you had the opportunity, drive, and ambition to acquire and read this book. All we can say is, "Keep it up!" Decide how many hours a week you want to spend on your career. Take 5 hours off the top and pay yourself first. Spend that time away from the office, reading books and magazines or writing software related to any topic that interests you. Make this practice as regular as your office hours. .....
I've heard of the idiom - off the top of your head. But what does off the top exactly mean in this context?