Number of candidates (n) is the number of candidates that have taken the test in question; so, the number of scores that has been achieved (since retests are not allowed this is also the number of first attempts). It is the true number; no selection is made. In interpreting this number one must realize that quality is more important than quantity in statistics. More is not better. A sample of 30 who have taken the test seriously, done their best, and honestly reported their personal information, is far superior to a sample of 400 who have taken a free online test carelessly, without striving for a good score, without reporting true information, and with some of them taking the test multiple times under different indentities (not to mention the inflated samples one obtains by mixing first attempts with retests). It is a popular fallacy about statistics that a large sample is better than a small sample.