I am sorry but what happens if say no 7 and 8 do not reach the correct number of points. If they qualify anyway what would be the point of a cut off

There isn't really a correct number of points. As MH said it's the "Top 8 players at year end. So to qualify you have to pick up enough points so that it's mathematically impossible for you to end the year outside the top 8".

The live rankings site does the maths for us, and the cut off figure will reduce as the weeks go by.