The different levels are actually interrelated; they don't refer to different kinds of "tasks."
So - you're 50K (vision, purpose) informs the 3-5 year goals you have at the 40K level, which in turn are analyzed so that you have projects associated with them. The same goes for your 1-3 year goals. Everything ties in, although not always on a 1:1 level. There's some wiggle room. 20K, or your Areas of Focus, are more of a "safety net," or a lens through which you can look at everything on your plate to make sure you're addressing the important areas of your life. This, again, won't be a 1:1 balance across all areas all the time.
If you're truly new to GTD, I would counsel you to stick with really understanding the relationship between the runway and 10,000 ft project level. Really get to understand the processing questions, and get so you're comfortable with Collecting, Processing, Organizing, Doing, and Reflecting.
THEN start to look at the upper levels and how they can inform your daily activities.