I think I got it now. The reason I saw history from other communities on my server is because others had subscribed (from my server) and started a history for my server from the time they subscribed. In this case now, I was the first and so no history. Is that correct?
Also when I see a very low subscribed number for a community on another server (from my server) it is because that number shows how many people from my server are subscribed only. When I visit the server where the community is hosted and see a large subscribed number, does that represent the total number of subscribed to that community across all servers or the number of subscribed only for the server that hosts the community?