I have no idea!!
But I track mine[what little there is!] pretty well. I am sure I am within a half hour of my actual sleep. REM sleep is the most important. And when sleep is interrupted numerous times during the night[like I experience], REM sleep suffers. I rarely get 6 hours[that would make me happy]. I usually get 4 or 5 hours which is not enough, especially since it is interrupted.I can also go through periods where I get 2 or 3 hours a night. It is hard to function with multiple nights of that little sleep.I do not like drugs so I just deal with it. We all have things to deal with,some much more serious than lack of sleep.