The method described in this thread is not correct - this should have become obvious when it was pointed out that such a system would allow a student to receive a mark greater than 100!
The 'pool of marks' description serves as a convenient analogy, but nothing more. It does not explain how the system actually works.
The moderating procedure is (correctly) explained in detail
here (using documents obtained from the Board) and you can test it out yourself
here (using a calculator we wrote based on the Board documentation).