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This article answer these questions as well:

• Why do I see a check mark on a unresolved issue?
• Why does an open issue that still in the work have 100% progress indication?
• When I turn on "Unresolved" filter button, why do I see some of the resolved issues anyway?

Answer

The JIRA's notion of a "Resolved Issue" (or "Completed Issue") can be quite confusing. The source of confusion is that an issue is considered to be resolved based on its Resolution field, not based on its Status:

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