In order to earn the "Ideal or Improved Blood Pressure" measurement reward within a month, you must record validated blood pressure measurement that is within the ideal blood pressure range (for both diastolic and systolic), or categorically improved blood pressure measurement from a previous value.
The ideal range for blood pressure is <120mmHg (Systolic) and <80mmHg (Disatolic). For more information on the other blood pressure categories, check out the "What are the category values for Blood Pressure?" article.
Check out your "How to Earn" and "My Rewards" page on Virgin Pulse member website to see if the "Ideal or Improved Blood Pressure" reward is offered by your sponsor, and see other rewards available for measurements!