What is effect of training spam as spam?

I apologize if this question is answered elsewhere, but I couldn’t find it in the manual or elsewhere on this forum.

SpamSieve is doing a GREAT job flagging the 100-150 spam messages I get every day. Probably 90% are gray. But I do occasionally get a spam item colored blue or yellow or red.

If I select those messages and then choose, “Train as Spam,” does that improve SpamSieve’s ability to flag similar, future messages as spam?

Yes, but there are other potential bad side effects from doing that. I recommend only training messages as spam if SpamSieve did not think they were spam at all.