Do you need the overall cut-off point or the weighted cluster points.
-As for the overall points needed to join University say a B of 63 or 64 points, there is no formula used. JAB merely sits and looks at the available capacity in universities and looks at the number of candidates that fill the capacity and then the cut-off point is set.
-As for the weighted cluster points for the selection to specific courses, there is a table which you can use to readily see your weighted cluster points. The raw cluster points (individual grades for the four subjects most appropriate to pursue a course) are listed in a raw and the overall aggregate points( e.g a B+ of 70 points) are listed in a column. The weighted cluster point is where the raw and the column would intersect. I don't know the exact formula as that is advanced statistics but the tables are readily provided by the joint Admissions board.
Here is the link to the table.Its in pdf format.
Alternatively ,go to the link below
You will see a link "Students"
There is a drop down menu on it,
Then click on "calculation of weighted cluster points."
You should see the pdf table with the points.
The website also has overall cut off points and you can see the cut-off points for previous years.
Otherwise, I hope I answered your question.