Create an item that is an hourly charge.
Create a time tracking entry for say 8 hrs.
Create an invoice for the 8 hours.
Add another time tracking entry for 4hrs.
Try to create an invoice.
Since the 4 hours to be invoiced is less than the 8 hours already invoiced, the app thinks that an invoice should not be created.
In the Recaulculate button actions (On the bidget/Contract screen) the script to calculate the Accum B-Qty filters time tracking entries to only include
~ Method user / partner since 2008
~ Over 15 years field service experience
~ 2013 Method Partner of the Year
~ Degree in Computer Science