Sleep duration is way off

Hi there, just downloaded the app. I noticed the sleep duration compared to what Apple Health says is way off. I got 7 hours 9 minutes of sleep, while Body State says 4 hours 48 minutes? Changing the source to Apple Health instead of Apple Watch (which is default) makes it even lower to 2 hours. Any ideas what causes this? Have an iPhone and Apple Watch SE 2, all OS up to date.