Duration is shorter, length is wrong
The Sleep Duration is total sum of all your sleep phases (Light, REM, and Deep), not counting the awake phases - because when awake, you are actually not sleeping.
So on default settings, the Sleep duration is always a bit shorter than the duration of tracking.
If you wish your Sleep duration is the same as tracking duration:
Disable the awake detection in Settings → Sleep tracking → Awake detection.
You can also try to adjust the sensitivity of each type of settings to get optimal results. In most cases, too much awake periods are caused by significant HR peaks.
If you are not sure, where those awake periods come from, please use Left ☰ menu → Support → Report a bug, and send us the application log.
Tags: tracking, actigraphy, graph