A lot has changed on steemit during the recent few months, so a lot of information has become outdated. In general, if you see your upvote increasing by much more, it probably isn't, it's either a. someone else upvoted it, or b. the value of everyone else's upvotes have become worth more. In general, if the price of bitcoin goes up or if the exchange value of steem/steem dollars to bitcoin goes up, the value of people's posts and votes go up. The opposite is true if any of those values go down. The reason you sometimes see that your upvote does a lot is becuase the price updates when you upvote (along with when you vote). So if you clicked on a post one minute ago, and saw the value, and then you read it and gave the upvote, the price may be slightly different, or significantly if it is one of the top posts in trending. Some more important information is that payouts take one week as of right now, 75% goes to the author, and 25% goes to the voters. A combined half of what the author gets is steem dollars/steem, and the other half is steem power which can be withdrawn over 13 weeks once you half around 10 times (I believe) the starting steem power value of your account (not including the delegated steem power, which is the power that you see as a + (amount). I hope this helped!