Do you mean the export shows different data than what is shown in the app?
If you pause the timer a work unit that goes over midnight, the app currently cannot tell when exactly you did pause it (before or after midnight) and then puts as much time as possible in the day before midnight and the rest after midnight. In other words, the app doesn't store the timestamps of when the timer is paused and resumed. In sum, there should be no "work duration" being added or removed