Amazon Brand Registry

I have a question about Brand Registry. My lawyer told me that when I file for Brand Registry with Amazon I will need to provide pictures to Amazon with the logo on either the product or packaging. If the FNSKU has to be on the packaging box and you get that AFTER you list a product, How in the world can I have the correct SKU on the packaging box if I don’t get that until AFTER I list my product??? Won’t Amazon see the wrong SKU on the packaging box if I just make it up and deny my application or something?? Or am I thinking too far into this and as long as your packaging has your logo, pictures of your product, and looks legit it doesn’t matter what SKU code is on there??