Results of tracked sleep staged changes

[Judiiths]

In the morning, my Fitbit versa shows me my sleep stages, and tells me, for example, how I slept for 8.15 hours and was awake for 42 minutes the past night. Later during the day though, these results sometimes change. All of the sudden I only slept 7 hours that seem night. The graph of sleep stages remains the same. What is happening here?

[Rich_Laue]

Maybe a screen shot would help us see what you are seeing.