Quoted from RobT:So many factors go into rating a pin, including how much time you've spent on it. What's a fair amount of time? Most of the pins that I've rated I've owned, so you'd think those would be valid. But as others have said, you often tend to rate the ones you own higher (I'd like to think that I don't do that though). So how much time should you spend playing pins that you don't own before being able to make a valid rating?
I dunno but you can also change your rating at any time. I rated BSD kind of low after playing it 3-4 times. 3-4 months later, being a better player and having watched Bowens tutorial, I understood the game more and rewrote my initial rating. I dont think I will change my Godzilla rating anytime soon though lol.