I work in the medical field and have experience with BP machines. You've just discovered a little secret about BP numbers, they vary constantly. You need to measure exactly the same way, under the same conditions everytime to know if your numbers are moving. When I am testing a cuff, as I did just today, I can raise my systolic by30+and diastolic 20+ simply by holding my arm parallel to the floor, rather than straight down. I can raise it as much or more by putting the cuff on my forearm, or simply using to wrong size cuff. Always take it sitting, with at least 5 min of sitting quietly first.
Hope this helps. DLB