The "squeezng" is to be sure the cuff has gone high enough to block blood flow through your artery, regardless of which artery. If it mdoesnt do that the measurement is meaningless.
The systolic pressure, the upper number, is recorded when blood pressure in your artery is higher than that in the measuring cuff. If a physician takes it using a stethoscope they listen for the first sound as blood courses through the artery. If a machine it senses thst push of blood. If you look at the meter, you can see the indicator swing a little.
To be reliable, sit quietly in a chair with the cuff close to the level of your u r heart, use the left arm, be sure you do not cross your legs, keep both feet on the floor.
