Sales by Store report calculate Value Sold without taking into account order item quantity. See the first screenshot. It was 2 orders for the same product priced at $10. One order had 1 of the product, second has 2 of the product. Sales by Store report display correct quantity sold 3 and incorrect value sold $20. I guess it should be $30.
The Second screenshot illustrates result after the patch.
Patch is tested with trunk and 16.11. This bug exists from the very beginning. Perhaps this is not too valuable report if the issue left unnoticed for so long time. But I have been asked about it twice recently and I think it's time to fix it.