I believe he is talking about payment terms like "net 30 days". A made up example: Walmart buys a can of beans and promised to pay the seller 30 days later. During those thirty days, they buy five or six more order of beans to make up for that first sale and the other ongoing sales, each payment being thirty days later. During each of those 30 day periods, that cash is sitting in Walmart's pocket for them to invest etc.