NJKScrollFullScreen bottom boundary is wrong?

My Problem is: I set contentInset of my scrollView instance and isOverBottomBoundary never become true.

NJKScrollDirection currentScrollDirection = detectScrollDirection(currentOffsetY, _previousOffsetY);
CGFloat topBoundary = -scrollView.contentInset.top;
CGFloat bottomBoundary = scrollView.contentSize.height + scrollView.contentInset.bottom;

Do I need to consider the height of ScrollView?