I had one read 82% at 11:00AM and didn’t learn until night when I checked my phone. I told my wife I wish my watch informed me I was about to die. Haha
Take out weird outliers I sit 95-100%
Blood Oxygen works well for me when i take them manually but I get anomalies when my band has loosened up and randomly takes it throughout the day. Hasn't been reliable enough for me to care about background daily readings to trust alerts if you drop too low. Maybe that is why you can’t set alerts?