It is natural in a logbook to want to keep data on your device after logging it.  In our Logbook Pro iPhone, iPad, and Android apps DATA serves no purpose as the device is designed to be an input system for new information to sync back to your PC while away from your PC.  Flights for example should be entered and synced to the My Sync portal and then purged.  In the case of pending flights (future flights) not yet flown, they should remain on the device until flown.  Once the flight is actually flown you can then update the information, remove it from pending flight status and save the update and then sync it when ready.  Again, once the flight is synced you should remove the information as it is no longer needed.  You can confirm your sync worked by logging in to http://logbookpro.com/sync (My Sync Portal) and verify the information is staged awaiting sync into Logbook Pro PC edition.

Reports on the device are not affected by data entered or removed on the device.  Reports are generated by Logbook Pro PC edition and sent to the device when synced providing more robust and informative reports based on your entire Logbook Pro history.  If you want reports updated while away from your PC you can enable Scheduled Sync in Logbook Pro PC edition.  For more information please refer to the documentation.

The only caveat to the above is Certificates, Ratings, History items that you may have on your device that you want to keep for future reference. 

To remove synced information tap the trash (purge) button (menu/purge on Android) and choose "Delete Synced" from the list of options.  You can also set "Purge Synced after Sync" in the Settings/Synchronization area if desired.