Burndown chart doesn't show scope change for issues that has two values in Sprint field

[Elena Oleksenko]

Situation:

We planned sprint and included not completed issues from previous (closed) sprint. The new sprint has been started and after some time we removed from this sprint one of the issues that was in previous sprint. This was not reflected in Burndown chart, scope does not changed, all looks like removed issue never was in this sprint. Is this expected behavior? 

[Troy Spetz]

We use JIRA 7.12 server version.

My suspicion is that the issue's Story Points are counted in the first sprint to which it was assigned.

Once you removed it from the second sprint, the points counted 'backwards' to the previous sprint -- without showing the SP drop in the second sprint.

Do you know if the total SPs *increased* in the first sprint, after you removed the second sprint from the issue?