Hi Wally:
I agree that English isn't logically exact and your example demonstrates that. I'm not even certain my one line explanation earlier was precise enough.

It doesn't help that the GridView syntax is a little cryptic, but unlike English, it at least has a defined set of rules.

I picture a large barrel and a smaller bucket. The barrel contains all of the orders that have been entered. Susan wants only the items that are i) Orders, ii) incomplete and iii) have a backorder quantity. The first 3 lines separate out those items and move them to the smaller bucket.

Now that they are in the bucket, she wants to filter them further. She wants only the ones belonging to Customer TD5775 OR belonging to any customer associated with Salesman KINGSN. The last 2 lines do that because they are in brackets after the "OR" operator.

In your example you would have transferred all Incomplete orders with a Backordered quantity belonging to TD5775 to the bucket. That's good. But the final part would have transferred all orders belonging to any customer associated with Salesman KINGSN regardless of whether they are Complete or have Backorders. It would also have included Invoice and Credit Note transactions. That would be a lot of records.

Susan's description of her goal could have been interpreted to mean that result. However it would have resulted in a meaningless report so the other interpretation was more likely.