I'm using some approximate times to simplify things, but my sleep log recently showed that I was asleep for 8 hours and awake for 1 hour. When I looked at my sleep log it showed asleep from 11:30pm to 8:30am, but the first 30 minutes of that it showed I was awake, so I actually slept from 12:00 to 8:30 with only 30 minutes of being awake. However if I edit my sleep log to say I went to sleep at 12:00, you would expect it to say I slept 8 hours and was only awake 30 minutes, but it actually says I was now awake for 58 minutes and only slept for 7 hrs 32 minutes, so reducing my actual sleep time by 30 minutes while keeping time awake basically the same. Why would all the other data change when I edited this sleep time? It's like it wants to convince me I'm awake more than I actually am.
