Talked to Apple Support. Pointed out to me that the lighter bands (Sunday) showed time period where I was still in bed 'sleeping' but something had changed (not specified). Said could have been me rolling over, faster heart rate, blood oxygen - who knows?
The darker bands I was 'SLEEPING'. the summary shows 9hr 31min in bed, with 6hr 30min asleep. The two small dots are colored to match the two band shades. To my eyes (age 72) the tiny dots colors look the same.
I have two suggestions that I will send to Apple:
1) fill color the two summary times areas with the appropriate color shade
2) provide some description if possible why the Watch/iPhone though I wasn't asleep during the 3hr 1min (cumulative) last night/morning.