Just select the "Normal" setting and click save. If any of the predefined values does not match the behaviour that you want, then change the value in the policy and click on save.
And, there is still some spam coming trough... is there something I can do?
You can adjust the scores (spam tag level 2) in the spamfilter policys to match your requirements. You can see the actual score that a mail got in the header of the email.