Beware these little home BP machines. I had severe hypertension and my licence was pulled 4 years ago at 180/120. I don't have white coat syndrome, and I'm afraid I don't understand people who do- I don't know what there is to fear from the procedure itself. I have been on medication since and took 5 months to get my licence back. I never found much correlation between surgery readings and my home machine. I think these little home devices are only good for spotting a trend and not comparing individual readings from different machines as you did. It all depends on so many factors. In the surgery, you want to be upright leaning/half sitting on a desk or bed in there, not lying down.
It may be possible you do have hypertension!