What does the narrator mean when he says, ''Our departure from Marlow I regard as one of our greatest successes"?

The men stop at the town of Marlow to shop for groceries in Chapter XIII. The narrator describes their venture in the paragraphs that follow this quote. They visit shop after shop and buy something in each one. Instead of being inconvenienced to carry the items themselves, or to have the baskets sent down to their boat, they employ the services of the local shop boys to carry their purchases and to follow along. J. describes the entourage -- which resembles a small parade -- with Montmorency, George and Harris near the front, J. at the rear, and a variety of boys, men, and dogs walking in between. “Our final march down the middle of the High Street, to the river, must have been as imposing a spectacle as Marlow had seen for many a long day,” he says. The scene, and the fact that they could initiate it on their own, serves to validate their mood and assumption of self-importance. And it’s a humorous image for the readers, at the same time. It is a great success, all around.