How it scores
The SpamAssassin score can be an integer or real number
required_Score = 5
required_Score = 8.2
Emails are marked with a number starting at 0. This is, in-a-sense, how spammy your email is based on a huge number of factors such as content and origination. A higher number means your email is very spam-like while a lower number such as 0 or 1 is a relatively clean email. Take a look at how SpamAssassin marks emails here: http://help.campaignmonitor.com/topic.aspx?t=104
There are some factors that subtract from the score such as verifying that your email is originating actual server. Your emails should ideally be under 5. You can find out how to increase your emails reputation here.
The number you should be setting for marking email as spam is set under “Configure SpamAssassin.” The lower the number, the more likely your email will be marked as spam. The higher, the more relaxed the filter is. Here’s an example: