What should I enter in line 10 of the W-8BEN form in itunes?

Question

Apple App Store

I am a sole trader and would like to sign up for itunes connect.
I find conflicting information about filling in point 10. Is it necessary to indicate the paragraph (first field), if so, which one?
Do in-app purchases fall under "Income from the sale of applications." Or do I need to fill in something additional below?