FAQ - Why use different totalling levels for the 2 counter fields?
The totalling level of a total field controls the point in processing at which it should be re-set to zero in order to begin accumulating for the next value of the sort control field. Unlike other totals, a running total can have a different value depending upon where you print it.
Our report is "counting" Warehouses for the entire report. When we print the first warehouse, it is 1. The value of the count field for the second warehouse is added to that of the first (i.e. the running total) and printed when we print the second warehouse. The re-setting of the report level total actually occurs at the end of all the data - when the "Report level" sort break occurs. We want the sequence to begin with the first record and continue unbroken until we have printed the last one. The report level running total will deliver this outcome.
In the case of the Product Number counter, the report is counting this within each Warehouse. When the Warehouse value changes, we want the counter to be re-set to zero to begin counting Products in the next Warehouse. The "Running total of Product Rank by Warehouse ID" delivers this outcome because when the warehouse changes, it is re-set to zero to begin counting products in the next warehouse.