Hi @roserivitar, That would be a great question for the sleep medicine doctor. There is a lot of different technical information available that tells you how the events are recorded but it's not so easy for the average bear including myself to understand.

Respiratory Event Detection by a Positive Airway Pressure Device: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3274337/

Rules for Scoring Respiratory Events in Sleep: Update of the 2007 AASM Manual for the Scoring of Sleep and Associated Events: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3459210/

If I understand it correctly, it's just recording changes of air volume/pressure the machine using sensors and mathematical algorithms to come up with the events per hour. So even though you only recorded 40 minutes worth of time using the BiPAP it saw an "average" of 70 events. It does beg the question if the machine is calibrated correctly or if there is an issue with the settings which would be a great question to ask your sleep medicine doctor.