Amazon Seller Error Code 5461?

I was creating a “dummy listing” on amazon before doing an active posting for my first product and got this message: “5461: you may not create new ASINS for the brand ___. if you believe the product you want to sell is not already listed in the amazon catalog submit form…”

I purchased a UPC barcode yesterday for my product and am not sure what this error message means? there are some products on amazon very similar to what i’m selling, but i’m not selling anything from someone else’s brand.

what does this mean?