Placing a Running Count on a Report
This procedure explains how to place a running count of items on a report that produces something like the following. Note the sequence of numbers at the left of each Product ID.
Create a calculated field. In this case the name is running. Its expression is run_count(product->product_ID). You could count any item on the Detail section of the report.
Drag the new calculated field from the Drag and Drop list and place it on the report.