Average in tests like that is generally 100. 100 is the center of wherever the vast majority of scores fall. The further away one is from 100, the less "average" you are in comparison to everyone else that has taken the test.
Exactly what 100 actually represents changes as the population changes.
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I'm not likely to be around much longer. As before when I first signed up here years ago, I'm finding that after a long hiatus, and after only a few days back on here, I'm spending way too much time here again already. So I'm requesting my account be locked, banned or whatever. It's just time. Until then, well, I dunno...