I believe this is how it works;
There are 7 contestants left. The highest scoring from the judges is awarded 7 points, the second highest 6 points and so on down to the lowest at 1 point.
When the public vote the contestant whogains the highest public vote is awarded 7 points, the next highest 6 points and so on down to the lowest at 1 point. The points awarded from the judges rating are added to the ones from the public rating and so the contestants positions can change order.
The contestants at the top of the leader board after the judges marks should be reasonably safe but all the others are vulnerable.
Does this make it any clearer?