Best thing to do is take your machine with you to the next Dr appointment.
Have them check you blood pressure then check it on the machine...
I have two machines now, just got a new one.
I used them both and they were only a few numbers apart from each other but the pulse was right on.
I like OMRON brand myself, don't go cheap....
Electronic BP machines can often give inaccurate readings, but not by much. I have both; a machine and a cuff.
I would think you should be able to monitor your BP readings at home. Do you have high BP? Did you doctor tell you to take it at home?