The systolic blood pressure number is always said first, and then the diastolic blood pressure number is given. For example, your blood pressure may be read as 120 over 80 or written as 120/80.Blood pressure is measured in millimeters of mercury (mm Hg).he diastolic blood pressure number or the bottom number indicates the pressure in the arteries when the heart rests between beats. A normal diastolic blood pressure number is less than 80.