There are a couple of different ways that something like this can happen. The most common reason is that one of the users edits the Time Item after the Invoice has been generated. What will happen in this scenario is that the ?main invoice? will remain as it looked when the invoice was created. The ?Detail of Time Charges? page will then be changed. The ?Detail of Time Charges? page looks at the current condition of the time entry to generate how it prints. If the user makes changes, the invoice itself remains unchanged, but the detail can be updated.
Another scenario that can make this happen is based on what I had mentioned above? if the user uses the ?override? button to force the system to create an invoice for a certain amount, the main invoice page will show one figure, but the ?Detail? page will still display the ?old? total. If the user were giving them a discount, this approach would allow the user to generate the invoice for the appropriate amount, but the ?Detail? page would be off.
The last reason is that potentially the user was invoicing the item a second time. If the user joined their time to an item that was already invoiced, the item would appear on the ?to be invoiced? list. When they invoice that item, only the ?new? entry amount would be billed to the client and would show on the ?main? body of the invoice. However, the ?Details? pages will still list all of the time associated with that item.
In summary, this can happen, and the ?main? invoice will always remain unchanged because it is an official tax document, but the detail page does have potential to change.