You have multiple blacklists and would like to know how internet blacklists in Kerio are used. Specifically, you would like to know whether only one score from one list is taken into account.
All blacklist scores are taken into account by adding them together. In the example image below, if a sender was found in both SORBS RHSBL and the SpamCop blacklist, then the Spam Score for that email will be incremented by 2. If it is only found in one, then the spam score gets incremented by one.
Note: This is just an example, please use the settings and values which work best for your organization.
Further details on blacklists and whitelists can be found in this article: Email Spam Protection using Blacklists and Whitelists