Pure Message rules and scores/weights

Does any one have any info on how to read the PM rules / scores / weights applied to messages? I need to identify why some messages are attracting scores but, the X-Headers don't really explian to well.

I get a score of 25 for some messages with the following but, can't tell if all thse rules contribute to the score, what they mean or how any applied score is weighted.

PHISH_SPEAR_HTTP_RECEIVED 0
FROM_NAME_PHRASE 0
__TO_MALFORMED_2 0
__TO_NO_NAME 0
__MIME_VERSION 0
__CT 0
__CTYPE_MULTIPART_ALT 0
__CTYPE_HAS_BOUNDARY 0
__CTYPE_MULTIPART 0
__HAS_X_MAILER 0
__HAS_LIST_UNSUBSCRIBE 0
__HAS_MSGID 0
__SANE_MSGID 0
__HAS_XOAT 0
__ANY_URI 0
LINK_TO_IMAGE 0
__URI_NO_MAILTO 0
__FRAUD_MONEY_VALUE 0
__FRAUD_WINNER 0
__CP_URI_IN_BODY 0
__CANPHARM_COPYRIGHT 0
__FRAUD_LOC 0
SUPERLONG_LINE 0.05
__CANPHARM_NEWSLETTER_MSG 0
__HTML_BOLD 0
__HAS_HTML 0
BODY_SIZE_10000_PLUS 0
BODYTEXTP_SIZE_3000_LESS 0
__MIME_HTML 0
__IMGSPAM_TABLE_1 0
__TAG_EXISTS_HTML 0
__URI_NS 0
SXL_IP_TFX_ESG 0
HTML_70_90 0.1
HTML_FONT_INVISIBLE 1.0
__FRAUD_MONEY 0
FRAUD_X3 1.667
IMGSPAM_TABLE_1 0
WEBMAIL_SOURCE 0
__HAS_LIST_HEADER 0
BULK_EMAIL_SENDER 0