[exim] incorrect processing of negative spamassassin scores

Hi all,

some of the support staff I'm working with seem to think that the
following config is incorrectly flagging a message with a negative
spamassassin score as if it were a positive spamassassin score.
For example a message with a -4.1 spamassassin score is being tagged as
if it were a +4.1 spamassassin score.

My config is not much different that the default config examples except
that I am using a macro for the thresholds
(yes I know technically they are strings, not integers. Is that where
the problem lies)

any help would be much appreciated,

Jason _Meers

Macros defined as:
  MACRO_SPAM_REJECT_MESSAGE_AT    = 90
  MACRO_SPAM_TAG_GROUPWARE_AT     = 50
  MACRO_SPAM_TAG_SUBJECT_AT       = 40

Acl section of config:
# SPAMASSASSIN CHECKS HERE

# add new header for groupware servers if spam score is greater than XXX
warn    condition = ${if >{$spam_score_int}{MACRO_SPAM_TAG_GROUPWARE_AT} 
{1}}
    add_header = X-Spam-Groupware-Server-Spam-Flag: YES

# add new subject if spam score is greater than XXX
warn    condition = ${if >{$spam_score_int}{MACRO_SPAM_TAG_SUBJECT_AT} {1}}
    add_header = X-New-Subject: +++ SPAM +++   $h_subject:   
SPAM-SCORE=$spam_score

# Unconditionally add score and report headers
 warn    add_header = X-Spam-Serco-Score: $spam_score\n\
                  X-Spam-Serco-Bar: $spam_bar\n\
              X-Spam-Score: $spam_score ($spam_bar)\n\
                      X-Spam-Report: $spam_report

# And reject if the SpamAssassin score is greater than
"MACRO_SPAM_REJECT_MESSAGE_AT"

 deny    condition = ${if 

>{$spam_score_int}{MACRO_SPAM_REJECT_MESSAGE_AT} {1}}

         message   = Your message scored $spam_score in our spam filter.