Your machine gave you a bad reading. It is possible to have a diastolic pressure of 20, but to have a systolic pressure of 110 and a diastolic of 20 is highly unlikely. Electronic BP machines, especially non-professional models are notorious for being inaccurate.
checking" on an electronic BP cuff just feels for your pulse while it is inflated; if your pulse is irregular, it tells you that you have an arrhythmia. You can do the same thing by feeling your own pulse.
This feature is somewhat accurate, however, it is possible to have an irregular heart rhythm and not have a problem. A lot of people have what is called Sinus
Arrhythmia, which is benign.