- All (but maximum 3000) of your artists who lack biography, similar artists etc are picked, and last.fm information is fetched.
- 3% (but maximum 1000) of your artists who have biographies, similar artists etc are picked (chosen by having the oldest information), and the last.fm information is updated.
This means that if you have a library of thousands and thousands of artists, biographies, pictures, similar artists etc might not get fetched for all artists during the first library scanning. To get information for all artists, you'd simply have to scan your library again.