I use a ResMed AirSense 10 machine, but do not use the MyAir feature. However this would be my guess as to what it is reporting.
The first Events reading shown as 2.4 events per hour (AHI) in this example is the total obstructive apneas, obstructive apneas, and hypopneas divided by the number of hours the machine was on. The general goal is to be under 5 AHI.
The second Events I think just shows how many sleep sessions there were during the night. The machine records each sleep session separately and totals the events for the AHI reading. I am assuming one on off event would be if you just put the machine on, slept through the night, and took it off in the morning. In the example above it shows 2 events, which would suggest the machine was off once during the night, so there are two sleep sessions.
My preference is to use SleepyHead to display the detailed data. It gives you much more information than MyAir does.
The AirSense 10 machine also can also display a more detailed report if it is set up to do so. If you are interested, I can tell you how to set it up.
As I said I do not use MyAir, and am guessing a bit. From what I see in SleepyHead I am thinking it is just a session count. If you look at the screenshot below I took from my wife's data when she was having some issues with her mask hose coming apart, you can see the session data in the bottom left. It lists the start and stop time of each "session" during the night. SleepyHead gives you the option with the little switch to the left of each session to turn it on (green) or off (red). This is helpful if you have the mask on for testing the seal or something and don't want to display that part in the graphs. For that night of my wife's she had 4 sessions, each with a start and end time. I take it if those results were displayed in MyAir it would show 4 on-off events. Quite crude compared to SleepyHead, but I guess it does remind you how many times you either got up for a P or had mask issues...
