Available on desktop and the iOS app, you'll see the Time Divider, a nifty little underrated feature which can be very useful in managing your day.

You can move the Time Divider up and down, above or below tasks, and what will happen is only the tasks above it will be captured in the List and End times.

If you've only got 3 hours to work this morning, or have to finish work at a specific time, move the Time Divider up until you see the time that works reflected in the List and End time in the bottom of the task list (desktop), or at the top (iOS app).