The word "accurate" was the wrong choice of words. The machine itself is always going to be "accurate" if it's working correctly, and cuff is used right. Perhaps "proper" was a better word, since we're not talking about the accuracy of a measurement.
Since you'll get a higher readout after exercise, or even moderate daily activities, it's recommended that the person be perfectly relaxed for a few minutes before taking the reading. What I described is just my way of being perfectly relaxed, and what I know for a fact doctors do if they suspect an actual BP problem, and want to "scrutinize" it to find the true lowest resting reading.
Since you'll get a higher readout after exercise, or even moderate daily activities, it's recommended that the person be perfectly relaxed for a few minutes before taking the reading. What I described is just my way of being perfectly relaxed, and what I know for a fact doctors do if they suspect an actual BP problem, and want to "scrutinize" it to find the true lowest resting reading.