Time of Day, BP rises through the day. Measuring technique varies...sitting in chair?, crossing legs? arm height heart? etc Complete list of what not to do here:

https://www.dietdoctor.com/blood-pressure#athome

DH was told to take the reading at home shortly after he woke, before he moved around too much, drank coffee, etc. in other words, do it at same time under same conditions and early in the day so it was not influenced by however your day went.