In goods and services markets, households buy finished products from firms that are looking to sell what they make. In this transaction, money flows from households to firms, and this is represented by the direction of the arrows on the lines labeled “$$$$” that are connected to the “Goods and Services Markets” box. (Note that money, by definition, flows from buyer to seller in all markets.)
On the other hand, finished products flow from firms to households in goods and services markets, and this is represented by the direction of the arrows on the “Finished product” lines. The fact that the arrows on the money lines and the arrows on the product lines go in opposite directions simply represents the fact that market participants always exchange money for other stuff.