From ula on 2016/10/08 15:07:59 +0000
At recording start it is technically not possible to distinguish between light sleep and awake (trying to fall asleep). If this awake time at the start was longer, then the smart alarm may ring unnecessary early.
For peaple with short last sleep phases (shorter as smart period) it results in alarm by first (of 2 or 3) opportunities - long before end time; and before the real optimum is reached.
Copied from original feature request: http://urbandroid.uservoice.com/forums/264867-sleep-as-android/suggestions/16558468-start-of-1st-deep-sleep-as-reference-for-smart-ala