Online I'm not finding specification as to the range.  Our current monitor seems to not work after 150/90.  We've had it to a couple of doctor office visits to check against their equipment and it's as accurate as needs be.

My wife will go above that in the doctors office, "white coat" syndrome is what they call it.  Here at home her range is what is referred to as normal much of the time but it spikes and then comes back.  We would like to be certain that those spikes aren't in the danger, go see a doctor range.