Currently for each task, we can add the original estimation and then add spent time.
The burndown chart shows the 'Remaining Effort', which seems to be : estimation - spent time.
However, this is not always accurate. You may realize at some point that you need more or less time to actually finish the task. In Jira, you have the option to specify the spent time and then specify the remaining time.
How to achieve this in Youtrack?