When you've accomplished something as significant as having an Amazon Best Seller, in this competitive market, you should strive to herald that accomplishment wherever and whenever possible. This is now part of your branding and promotion. Getting Amazon Best Selling Author status is the result of hard work and is something to be proud of. It is a credential that once received can be used forever. As such, it should be proudly displayed by using the Amazon Best Seller Logo on your book, your website and any promotional materials you develop. Your reader may not know it took sales of 100-500 books in a day to reach that status, but what they do know is that the book is a good gamble to spend their hard-earned money on. It is a stamp of approval that the reader looks for. And it doesn't matter if you are an overall bestseller or a best seller in a particular genre. The reader just wants you to be the best.