Once your customer is confident an option fits their needs, it is, nevertheless, still possible to lose the sale. The customer may get distracted, or the check-out line may appear too long.
The best way to avoid losing the customer is to lay out the next steps to helping them leave happy. If the sales rep above has confirmed that the shirt fits, the client likes it, and any other items they want or need have been gathered, bring the sale to completion by clearly stating how to make the purchase, "It looks like we got you everything you needed today. Let's take you to the register and get you checked out."
Salespeople need to understand that helping a prospect is like going on a journey together. They need to start at a meeting point, discuss where they are headed, agree to travel together, and finally, arrive at the destination.