I was at Google for about 10 years. Here’s my take on the levels.
L3: How well do you do what you’re told?
L4: How independent are you? What’s your individual impact?
L5: How deeply technical are you? How well do you influence others on the team? What do you own?
L6: What’s your reputation in the greater org? How is the product area better because of what you do? Why aren’t you a manager of a 10-person team yet?
L7: How is the company notably different because of you? What technology did you create that most everyone knows about? How have you made a difference in Google’s quarterly revenues for your product area? Why aren’t you a manager of a 30-person group yet?
L8: Why do you have the final say on whether the product area moves forward on any given idea? What books have you published? Which VPs regularly consult with you? Why aren’t you a director of a 200-person org yet?
Would you be ok with sharing your informal take on the other levels?