Ive used mine two weeks, im fairly new.
I downloaded the sleepyhead software and i was able to see how i was doing, if i had leaks in my mask, etc.
I dropped my AHI to approximately 5, i was 26 without cpap.
I actually feel more sleepy when i wake up, I feel is harder to wake up from such a deep sleep
in the afternoon I no longer need a nap, I no longer yawn and feel im falling asleep at the wheel in the afternoon, and that strangr headache (that later i found out it was due to the oxigen depravation) has gone away.
I have bad nights, im still making adjustments such as my humidifier, mask type, sleeping position.
But i had a change since night one, I think you should be able to drop your AHI lower, 20+ sounds high