Boss instructs employee to clock out whenever he's not actively working: 'My goal is for you to have zero down time.'

That's not how having a job works. 

If you've ever worked in retail or food service, you know that you seldom get a minute of rest in those positions. They are designed to extract as much labor from employees as possible while paying them as little as possible. There's often a list of all the extra things employees can do when there aren't any customers to attend to. You could reorganize the merchandise or restock depleted products. Even if you do literally everything on the list of "things to do when there's nothing to do," your boss will still find something for you to do, because standing around when you're on the clock is an unforgivable sin. 

Even if you're not technically "doing anything" at your retail job, your presence is "doing something." Without employees to man a store, anyone could waltz in and take all the merchandise! Store owners need employees to sell their wares because AI can't do so yet. If nobody comes into the store to buy anything during an employee's shift, that employee still deserves to be paid in full! If anything, manning a store with no customers is more taxing than manning one with a revolving door of customers. At least in the latter scenario, the time goes by quickly! 

The boss in this story wanted his employee to clock out every time he wasn't actively working. The boss thought this would be an incentive for his employee to constantly work throughout his shift, but it raised red flags instead.