I've notice that the time shown for "sleep' does not include the "awake" time which is part of the sleep cycle. Since we can awake about 30 times a night for 1-3 minutes this is a significant portion of the time in bed sleeping.
It's normal to see awake minutes in your sleep stages; studies have shown a typical adult could wake up briefly between 10 to 30 times per night (source). You may not remember waking up since you likely fell right back to sleep, especially if you were awake for less than 2-3 minutes at a time.
