Whether you archive or not depends on the Key Result.
Archived KRs are those KRs that are no longer necessary due to restrictions (time or scope, for example). Therefore, it makes sense that they are not counted towards progress, as they are not actively worked on and are no longer deemed a good way to validate your Objective.
On the other hand, when you've achieved or partly achieved a KR, it makes sense to keep it open because it counts towards progress and validates your Objective. It is also valuable not to archive it as it provides important context for future reference.
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