J.K. Adams Professional End Grain Walnut Board - 20" x 16"

We bought the carving board, brought it home and wiped it to see that the rag came up brown…
Applied the mineral oil as per instructions and waited until perfectly dried (48 hrs) cut bread on it and the crust had some brown on it… wiped the board with a damp cloth (which came up alarmingly brown still and let it dry.
applied another thin coat of mineral oil based on the instructions etc.
waited 48 hrs to be sure very dry… cut an onion and some brown on the food… so returned the carving board. Could not get my money back as the store policy is that anything used cannot be returned- however they eventually agreed on a credit.
Considering there is an obvious issue with the board I was surprised of the store's stance on the matter. The concern is not based on usage but clearly on some flaw of said board. ( I am sure of this as I now bought another carving board elsewhere of a different company of course and there is absolutely no issue before or after applying the mineral oil. )
So disappointed in the overall experience. I still want my money back under such circumstances. Waiting on the store’s reply.