The release burndown chart report list issues under the same sprint if the issue is under the same release version.
However, if the issue is not added under Sprint, the report still adds this under the recent sprint making this a vague report.

Can we add information to such cases stating that they are not under Sprint but have the fix version updated so that this gets meaningful report?

How to reproduce the issue:

• Create a project with 2 issues
• Create a release and a sprint
• Add the release to both the issues
• Add 1 of the issue to the sprint and leave the other in the backlog
• Mark both issues as done and complete the sprint.
• Now, the Sprint report shows just 1 issue that was completed under that sprint
• Shift to Release Burndown Chart and we could see both the issues under the same sprint

This creates confusion in the reporting assuming that the issues were completed under the sprint, however, the issue will not have any history about the sprint.