number of recent topics in "Feed" view

I'm using the new feed view (not to be confused with the older "fuild" view), where each section (forum) shows recent topics from that section.

Some forums shows 5 topics, while others shows less - sometimes even just 2 topics.
It doesn't seem to be related to the last update of the topics, as the 5-topics forums shows topics that are older than the ones found on the 2-topics forums.

What is the logic of this? is this limited by last update? date created? something else? Is there a way to control this?