Wholesale Discount: This is what the distributor or wholesaler purchases the book for. This is not the price that a retailer pays for the book.
Retail Discount: This is what the retailer purchases the book from the distributor/wholesale for. Each retailer has a pricing agreement with the distributor, and that agreement is not something that we as the publisher are privy to. They consider that private information, as it is in a contract between themselves and the distributor. This means, unfortunately, that each retailer gets it for a different price and we have no way of knowing what that may be. Rest assured, this in no way affects the royalties earned per unit sold, as that price is set by you and the retailer is required to pay that once a book is sold.
Retail Price: This is the price that the author sets for customers buying the book (from a retailer).
When an author or publisher sets their book at a 53% discount, this falls in line with what trade and academia publishers set their books to. The distributor is the entity that receives that 53% discount, their requirement for listing the book as available to brick & mortar stores, and then they offer your book at a discounted price that aligns with their pricing agreements with the individual retailers. This pricing agreement will be listed as "REG" on the distributor's page. Any reliable retailer will know their own agreements with distributors and be able to easily look at your book with the title and ISBN alone.
When a book is listed at a 40% discount, this falls in line with what online-only books are set to, and these books are not available for purchase to brick & mortar stores. The distributor is the entity that receives that 40% discount, their requirement for listing the book as available to online retailers, and then they offer your book at a ~20% discounted price to the retailer.