The "Consider spam at score ___ (-999.0 throught 999.0)" setting is the value or score at which an email message is considered to be spam. By default, the value is set at 7. You may wish to decrease this value to 5 or 6 if you are still receiving spam message just under the 7.0 threshold. However, it is highly recommended that 5 be the lowest number set for this value.
When a message has reached the "consider spam at score" value, the spam service appends the "X-Spam-Flag: YES" header to the email message. This is the header that your email client will look for when managing spam messages.