I can have as much as 30 pounds of pressure difference while testing both arms at the same time with a small change of pulse.
I'm talking like Left arm 82/48 pulse 79 then Right arm 122/63 pulse 58
Here's a post that addresses your questions from Dr. Weinrauch:
What if my blood pressure is different in both arms?
All the best,
Lisa Nelson RD
7 Natural Ways to Lower Blood Pressure