I was going to suggest this but white coat beat me to it. Technically a blood pressure reading should be after 5 minutes of sitting in a quiet room. You need three high measurements on three separate occasions. If you sprinted into your appointment and got your blood pressure right after you sat down, that's an inaccurate reading. There is an entity called white coat hypertension as well, where as the previous poster alluded to, your blood pressure is elevated in the medical setting but normal otherwise. The way to figure this out is 24 hour ambulatory home blood pressure monitoring. the device is a cuff you wear for 24 hours and it determines if you really have hypertension.
The cumulative amount of hypertension is what is really bad. Having a spiked blood pressure here or there is not that bad. And when you sleep, your blood pressure should go down. So really what matters is your blood pressure most of the day and most importantly when you sleep.
Here is a link to the JNC 8 guidelines which are the most commonly used in the US for hypertension.
https://jamanetwork.com/journals/jama/fullarticle/1791497