I'm a 1st year RN student & we did BP last semester and the main thing they always said to us was to recheck as it can be such an up & down thing I mean I could nearly hit some1/thing while out driving & have a high BP reading after a wait it would be normal.
Also that long waiting is terrible with a little one to chase after my doc has a long wait to I ring b4 I go now because 1 time I went and there were 7 people in front of me despite me being on time.