BAYES_00 BODY. Negative score?

[joe a]

Have some annoying SPAM that consistently shows a negative score on 
BAYES.  Is the default scoring or influenced by BAYES in some way?

*-1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1%
*      [score: 0.0000]
SpamAssassin 3.4.5

Thanks for any pointers.