Estimating Story Point

[M_ Nurfajar Ridla]

I have a lot of sub-task which distributed on some user story. On every user story defined story point estimation. By the end of the sprint period, not all of sub task on user story fully completed, How Jira calculate burn out of story point which sub-task uncompleted?

For example :
As user i want be able to........ (21 story point)
1. sub task-1 (in progress)
2. sub task-2 (done)
3. sub task-3 (done)
4. sub task-4 (done)

How Jira calculate burn out point story with 1 sub-task uncompleted?

Than you 

[Nic Brough -Adaptavist-]

It will burn down when what you committed to do (the story) is complete.  So there will be 0 burn down until then, at which time it will be 21.