OK! Thanks.

I see how I can set an item to "Not Junk" and I can see the optional "Junk rating" column.

I have not marked any items as "junk" so how did that happen in the first place?

Is that because a high percentage of users rated an item as junk (eg: 99%)?

I notice one can set Option -> Filter -> junk sensitivity. In my case that is set to about 1/3 the way from "Relaxed".

Thanks.