TrialOr is correct about what the top and bottom numbers (systolic/diastolic) mean.
In addition, the top number is often called the "stroke" number. Anything over 200 has a greater potential for a stroke. This is measuring moving blood through the body. This has nothing to do with your pulse or your heart beat. They may remain normal until you realize how high your blood pressure is and then they will escalate from fear and, in turn, drive the blood pressure up further.
The lower number (diastolic) also represents how much blood is at rest in the vessels.
So.....If you have a high pressure of blood surging through the body......and a high pressure of blood resting in the body.......
High blood pressures that go untreated have the potential to DAMAGE major organs like the kidneys, heart, lung, and brain. They are tissues that can only take so much.
THEN.....this damage can be called:
Kidney failure
Pulmonary Embolus (blood clot in the lung)
Myocardial Infarction (heart attack)
Stroke
I completely agree with Matt. It is not outrageous but keep an eye on it and get it checked again.