If you delete a transaction and then add a new transaction The Truckers Helper program is designed to display the next transaction number (following the previous transaction number) leaving a gap in your transaction numbers caused by the transaction you deleted. This occurrence is normal. The Transaction Numbers are used by the program to sort your records. It does not matter if some transaction numbers are missing.
If you want to order your records by date simply check the ORDER BY DATE box which is located next to the Transaction Number. To order them by transaction number (the order they were entered) uncheck the box.