I think this is not a fixed value as everyone's immune system is not working at the same efficiency to deal with infections.
As an example, I recently picked up a cold from a family member about two weeks ago I noticed that I was getting more hit values above 0.2 Threshold setting. When I am well, the hit values are mostly below 0.2 Threshold. My lower Threshold setting is 0.05 for BFB scans.
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