I don't know if this will help at all, and I understand that the use of certain multiple words for the same thing can be confusing. Especially since there is so much data involved in sleep apnea study.
I NEVER turn my machine COMPLETELY OFF , like an unplugged type of off. If you do that you may mess up your cellular communications system that is in the machine among other things.
I DO, however, hit the little power button at the top of the machine one time, each time I want to stop my therapy. I'll do this if I know I will be up doing things for any length of time. I know that each time I hit the power button in a 24 hour period all my "sleeps" will be recorded as SESSIONS and will appear as such in that left hand panel on the OSCAR report.
Once in a while I will take off my mask and leave the machine ON, not hit the power button at all, or unplug it or anything, and because I do not use the smart feature, I can get a lot and/or lengthy of leak reporting. In this case you will not have a separate session for this action.
I have no idea if this makes understanding any clearer for you, and I hope I haven't written anything incorrectly, but it certainly would help me if I were needing to know about off/on, start/stop.
Have I confused you? I am sorry If I have, but would feel good if it helped. (I have been helped so much here that I just was hoping I could pay it forward).
Regards,
Plmnb