If you're +-7 in your reading, don't panic yet. If you're there with a stage 1 or 2 hypertension diagnosis (130-140+ systolic), the margin of error discussed in this article isn't necessarily meaningless, but remarkably close to it - you need to address an issue there.
More as a PSA for you hardworking programmers and IT managers out there: if you have chronic hypertension, address it sooner than later. If you think to yourself that you'll start jogging daily starting next week, and your doctor is giving you the option for meds, just get on the damn meds. If you start an exercise regimen that can quantifiably manage it without the meds later, great. Don't let the perfect be the enemy of the good. Hypertension is the silent killer, and before it kills it contributes to all sorts of other bad problems and conditions.