Yeah, I just checked it out.
It's actually the previous THREE completed weeks, not four.
It also ignores the current week. Or at least it is ignoring mine as of Monday (game-time) morning. It may include it at some point during the week.
EDIT: Now, as of Tuesday morning, it's counting the current week too. So it's Current Week + 3 Previous weeks except on Mondays when it ignores the current week. We'll see if it holds true throughout the whole week.
EDIT 2: Yeah, it holds true for the whole week. It's Current Week + 3 Previous Weeks Except if the Current Week is Monday, then it's ignored and it's just the 3 previous weeks.