to me, SPO2 readings in the 90's is "normal" for most people and nothing to be concerned about. My average is 93-95 most of the time - awake, sleeping, pretty much all the time. I am in good health and decent shape. My father-in-law when I tested him was in the 98-99 all the time that he was just sitting around. He is in very poor health and very overweight and has much difficulty breathing. So,,. normal for one is not normal for another.
When to be concerned - typically an insurance company is willing to pay for O2 when you have SPO2 readings below 88% for greater than 5 minutes if my memory serves me.
In my original sleep study my numbers were in the low 80's most of the night. With treatment with the BiPAP I am in the mid 90's all the time.
Home this helps some