If it would be incorrect for a moderator to do anything in response to a report at the time when the report was made, then the report is considered inaccurate. Reports are explicitly marked as incorrect by moderators. It's also possible (though rare) for a report to be marked as neither good nor bad -- such reports don't count toward your accuracy percentage.

Average accuracy is 56%, so 60% (66% now) isn't bad. Unless you're only reporting really obvious stuff, very few people will have accuracies above 90%. Even if you have the correct mindset for moderation, you won't know the policies well enough until you've been a moderator for a while.