For example if your game is once in Top 25 and have a huge user base, the users keep your game on their iphones. Once you update your game they'll also update it, so you get big update numbers. But will this numbers be counted into the download numbers which affect your ranking in the app store? Can anyone help to answer this question?
Updates don't count towards your ranking position, neither do gift or promo code redemptions. Rankings only change every time your app is downloaded for the first time (ie purchased) from a particular iTunes account.
I think that they are to some extent counted towards ranking in the "what's hot" sections in game categories.. This is my guess from observation of my game only. Though I have also "observed" that being ranked well there doesn't do much for your sales