How should I read the margin waterfall?

Top down, as four questions rather than four numbers. After the goods: do the products earn? After logistics and fees: does an order earn? After advertising: does a customer earn? After overhead: does the store earn?

The bar lengths are drawn against net revenue, so the length is the margin rather than a shape chosen to look good. Whichever step loses the most is the one to work on, and it is often not the one that gets the attention.