In the configuration of Xpert-Timer you can have the program show an overview of all your timestamps when you shut down your Xpert-Timer. There you can double-check your entries again and make sure they are correct.
If there's a gap in your timestamps they will not be marked at all. If they are entered correctly, then you'll see a green bar on the left side. If the timestamps are overlapping the bar on the side is red. In our example, we have maximized the timestamp markers to identify the errors better.
You can also maximize those timestamp markers in your timestamp list. Just right click on an entry, choose "View -> Maximize timestamp markers".