Poco Junk Mail FAQ - Word lists and score values

Q: I'm just a little confused on the rating of junk mail. Will a index of +8, for example, guaranteee that the message is filtered or ought it to be -8?
You want to use a positive score to ban an item. From the junk mail words and phrases file "Enter words or sentences that should be allowed or disallowed inside the message body. Each entry can have a positive score (entry disallowed) or negative score (entry allowed)."

A score of +8 won't guarantee an item is banned though but it will come pretty close. In general all filter items are applies (as well I believe there are some other rules added which we don't see). The scores are added up for a message and if the score exceeds the junk mail tolerance you set then it is deemed as junk mail.