In addition to what @thediscocat and @marxrab said, you should also bare in mind that the estimated rewards for each post in your post listing are estimates of the total reward that post will earn both yourself and the curators. It may go up or down based on a number of factors, and you'll likely see about 75% of it enter your wallet.
Then, the estimated account value in your wallet is based on the 7day rolling average for the value of steem and sbd. If the price is dropping, the estimate will be too high, if the price is rising it will be too low. It only tends towards accuracy when the price is steady.
Hope this helps.