[Feedback] What is the "Active Communities" list based off of?

The new profile page has a sidebar indicating the user's "most active communities"

My current "most active" community is... The_Donald. But last week I deleted every submission/comment of mine from there from the past 6 months. So really, I haven't been active there for 6 months.

So when does the list refresh? I have made over 100 submissions/comments in the IcePoseidon sub the past two days, yet that doesn't appear in my active communities list.