Final answer:
The third critical piece of information on a product issue form is the date and time the issue occurred, which is essential for tracking and resolving product concerns.
Step-by-step explanation:
The third main item that must be included on a product issue form, besides a comprehensive description of the issue and the exact amount of product for which credit is being requested, is the date and time the issue occurred. This information is crucial for tracking purposes and helps in addressing any patterns of issues that may arise over time. Including the date and time on the product issue form aids in determining the urgency of the issue, the shelf life of the product, and helps in investigating the cause of the problem.