When you're taking your blood pressure readings and want to take another blood pressure reading to check for accuracy you should wait at least 3 minutes between the blood pressure readings.
If you do it right after then the blood pressure reading won't be as accurate.
Also make sure to lay your arm out straight and rest it on something such as a chair armrest or table and stay very still and quite while taking the blood pressure.
You need to be calm and have quietness around you when taking your blood pressure so if you have kids running around or dogs barking send them outside if possible or go into another room where you can have quite because that noise can cause stress which can raise your blood pressure and may not give you an accurate blood pressure reading.