I'm sorry—30 mmHg?

Maybe I am misunderstanding, or there is something wrong with my own knowledge, but "30 mmHg" added to systolic seems extremely high.

I am currently an EMT-B student here in the United States, and taking vital signs like blood pressure is our bread and butter. We practice it several times a week, on different people with different body types and different blood pressure baselines. Anything more than ±4 mmHg in a manual reading is terrible accuracy, and anything like +30 mmHg probably comes from someone who doesn't know how to use the equipment.

But again, maybe there is something I am missing. If there is I'd love to be educated and hear about it!