Losing points in lessons even with no mistakes

I am doing lessons in Attacks, "Essential Checkmate Patterns" and, when I find the solutions with no mistakes, I am losing up to 5 points on my rating.  Will someone please explain to me why this is happening?  This problem did not occur in the Tactics lessons.

Thank you.

• "Ultimately, it's not about the points but the learning - the points are a distraction."  

  I completely agree.  I've even told myself that with the result I've continued to wade through the 135 lessons in this course and lost  approx. 160 rating points.  Despite seeing my play improve through this ordeal, losing 2-5 pts. for a flawless execution of the lesson REALLY annoys me.  This course, Attacks, "Essential Checkmate Patterns" is the only time I have had this problem.  I suspect it is generated by the amount of time one uses to solve the problem or using the "Analysis" utility to test your moves before actually making the moves in the lesson.

  Thank you for your valuable comments.

Its about the learning, not the points.  As long as youre more concerned about the points, as opposed to the learning, you will slow your progress.

Yeah, I get that.  Thanks for your comment.

some lessons are time based. quicker the better.