To sleep: perchance to dream: ay, there’s the rub;
For in that sleep of death what dreams may come
– from Shakespeare’s Hamlet, Act III, Scene I

The Apple Health app that tracks my sleep every night, has been reporting only 4 to 5 hours of sleep for me, even after I had been in bed ‘sleeping’ for the most part of 8 hrs.
I generally feel OK in the daytime, so I believe I get more than 4 or 5 hours of official ‘sleep’.
For comparison with the Apple Health app, I’m trying an app called Sleep Cycle (screen shot on the right). The results from last night look encouraging (more accurate).