Customer satisfaction is the best indicator of how likely a customer will make a purchase in the future. Asking customers to rate their satisfaction on a scale of 1-10 is a good way to see if they will become repeat customers or even advocates.
Any customers that give you a rating of 7 and above, can be considered satisfied, and you can safely expect them to come back and make repeat purchases. Customers who give you a rating of 9 or 10 are your potential customer advocates who you can leverage to become evangelists for your company.