AWL confusion

[Rich]

Me new email host is using SA 3.0.1 and I have been watching what gets 
caught and what doesn't so I can do some user_prefs tuning if necessary. 
But I don't understand what is going on with this AWL stuff. The host 
service has it turned on and I get a non-spam message with this score 
report in it:

X-Spam-Report:
        * -2.6 BAYES_00 BODY: Bayesian spam probability is 0 to 1%
        *      [score: 0.0000]
        *   17 AWL AWL: From: address is in the auto white-list
So why on earth is a 17-score given to an address in an auto white-list? 
Shouldn't an address get a negative score (or, at least, a neutral zero) 
if it's in a WL?

Rich