Both numbers are equally important and you need both. There are two because you need both.
Explanation:
When you go to take your blood pressure the top number is the systolic pressure and it measures the amount of pressure in your arteries during the contraction of your heart muscle. The bottom number is called the dialostic pressure and measures the amount of blood pressure of you heart muscle between beats. Healthy blood pressures numbers are 120 over 80, or 120/80.
