I have to say early this year my medium readings did change... it used to be more and then it drastically dropped.

The accuracy you are talking about it could be that the math is coming from an array and they are not counting right. An array of 5 has the last item at index 4... first index is 0. If they are going by that it could make sense for the issue on their math. I can only guess here, maybe they decided to have AI build their algorithm... and they made a mess out of it (something I would not be surprised at).