OP- every test is scaled differently, and YES, it is a hard test. Here are 2 of my practice aamc's where I scored a 29 and 30. You'll notice that I actually scored higher with the 29 than the 30. (Got more questions right)
Guess it's kinda weird, but that's how they do it.
And no, a 30 isn't 66% for the MCAT (how we all wish it were!)-- more like close to 80%!