AND UA-767S Manuel D'instructions page 18

What is an Irregular Heartbeat
The UA-767S blood pressure monitor provides a blood pressure and
pulse rate measurement even when an irregular heartbeat occurs. An
irregular heartbeat is defined as a heartbeat that varies by 25% from the
average of all heartbeats during the blood pressure measurement. It is
important that you are relaxed, remain still and do not talk during
measurements.
Note: We recommend contacting your physician if you see this
symbol frequently.
%IHB is displayed as frequency of IHB detected.
IHB can detect not only noises such as physical movement but also an
irregular heartbeat. Therefore, we recommend contacting your physician
if %IHB level is high.
Number of detected
IHBs in memory
%IHB =
Display of %IHB: %IHB is displayed when displaying average values.
Level 0
%IHB=0-24
Not displayed
％IHB
Total number
(Refer to "2. Recalling the Data" in "Operation Mode".)
%IHB is not displayed when the memory number is
six or less.
Average value display
Level 1
%IHB=25-49
English 16
x 100 [%]
Level 2
%IHB=50-74
Level 3
%IHB=75-100