70% is the scaled score...This is what I got from wikipedia..

"A scaled score of 70 is required to pass the exam. This does not mean one needs to answer 70% of the answers correctly to pass, however. A portion of previous exam questions are then given on subsequent exams. After the exam, a statistical analysis of these questions is used to equate the new test to the benchmark test. This makes all of the tests more or less equal in difficulty."