Trip ETA can compute ETA for each cache in your trip based on a starting time you designate. Those times will show up when you download the trip into the Trip Assistant. As you progress through your trip and enter Arrived and/or Departed times for each way point, the ETA for the remaining way points will be computed and a message at the bottom of the screen will tell you if you are ahead of schedule, behind schedule or about on time. There is an option to speak the schedule status that you can turn on.

In the real world, your start time for the day often does not match what you planned (running late, breakfast not available until 08:00, etc). To correct for this, tap … and select the “Clear all ETA overrides). This will erase all the ETA values you manually put into the trip. Then when you depart the first way point, tap Departed and establish a new start time for computing the remaining ETAs for the day.