Using shy or short to indicate shortage
The order will be shy/short of 10 cases Either one works but you'll need to add "just" in front of both..IF you're going to keep "of" Otherwise, ..be shy/short 10 cases.
The order will be 10 cases shy/short Short. Never shy
We shorted the customer 10 cases Correct
We shorted the customer by 10 cases. Correct