The next of the special configuration settings for cards is the Show Effort option. By default, this option is checked, as shown here:
This option will show the effort on the work item. For tasks, this option is shown as Show Remaining Work. Talking about remaining work, it's also worth mentioning that the effort now has a similar edit experience on the board as the remaining hours did in TFS 2013.
Previously, you would have to open the work item if you noticed that the effort was incorrect, which was slightly annoying, knowing how easy it was to adjust the remaining hours on the task board.