The day and week view totals are based on your set day-start time, so it counts one "day" as day-start of one day to day-start of the next day. That means any entries that are logged before your day start time counts toward the previous day's totals. We do this mainly so that night sleep is displayed and counted for one day instead of split over two days. You can change your day start time on the Child profile page.
If you want to see 24 hour totals based on a 12am-12am day, you can see that for all categories other than sleep on the Summary view. Tap on the bar for any given day on the chart and the 24 hour total will show up underneath.