Respironics One 560P SD card question

I am totally new to looking at my data and this forum, so sorry for a simply question. Been using my machine for 10 months.

I found Sleepyhead a week ago and feel it is a great way to keep up with how I am doing. I have been exporting the data to Excel just to watch the numbers. One night I forgot to put my SD card back in the machine, but when I looked at the data (in Sleepyhead and Excel) there was information for that night with no SD card was inserted. There was no information for Flow Rate, but there were several data fields that had information.

What kind of data does the Respironics One 560P store when there is no SD Card?

Respironics machines record summary data in internal memory but not flow data. The SD card must be in the machine for the flow data to be recorded.

If you go into the P0 folder where the data files are located you will see 3 file types.
xxx.001, xxx.002 and xxx.005.
The xxx.005 files are the flow rate graph files and these are larger than the others and NOT stored on the machine's internal memory. So this data is lost if the SD card is not in the machine during the recording period overnight.

Now the other file types...the xxx.001 and xxx.002 are stored on the machine's internal memory up to a point.
These would be the summary usage data along with the other graph files ...like leak, etc.
These are stored on the machine for 30 days or so and then parts of those files will start being overwritten (oldest files first to go) and I don't know which of file types gets altered.

So some detailed data is even stored on the machine for around 30 days...summary usage (basic AHI and hours of use, etc) are stored on the machine for 1 year.