What is Activity in the Blog Activity Plugin?

In the blog activity plugin, just how is "activity" defined?

If I've got these statistics:

Updated blogs in the last:

Five Minutes: 1
Hour: 3
Day: 18
Week: 49
Month*: 78

Posts in the last:

Five Minutes: 0
Hour: 0
Day: 27
Week: 179
Month*: 636

Comments in the last:

Five Minutes: 0
Hour: 3
Day: 25
Week: 173
Month*: 381

What happened in that one "updated" blog in the last five minutes? It wasn't a post, it wasn't a comment...so what was it? What's the definition of "activity"?

(Also--as a request--this plugin would be hugely useful if I could pick a specific month, instead of just the last month. Is there another plugin that does that? Or an easy way to edit this one?)

Thanks for a great plugin, generally speaking!