Staging content of multiple sites

Hello, We have 2 instances of Kentico setup.We copied original DB and deployed second Kentico instance on it. Each instance has 3 sites. We would like original instance to copy its content to the second server using staging module. Here is what was done: 1) Setup original server as a source with documents, data, objects tracking. This setup is global for all sites. 2) Setup second server as a target. 3) On the original server in the cms desk addressed the sites like this: original_site1-> remote_site1, original_site2-> remote_site2, original_site3-> remote_site3. And here comes the problem. When I do synchronization of custom tables, which are enabled for Site_1 only, I expect those not being tracked for Site_2 and Site_3. But Kentico still does that and I have a lot of duplicated staging tasks.. Is this behavior expected? If so, how do I have to configure me servers to avoid this? We are running Kentico 6.0 Thank you!