m0useanswered grow question 2 years ago to be honest is a bunch of bullshit, easily manipulated, not a good metric of quality.
Its calculated by how many views, likes, comments, and other parts of a diary are filled in. If your trying to increase it fill in any box that's empty with data. if someone comments reply to it shows its engaged ask a question upload lots of pics/videos, win a trophy.
Good Luck!