I worked as a student in a factory for years, the rules was that if you're 2 minutes late, you have to work 15 minutes extra. But the same for 1 minute or 14 minutes, you only got paid per quarter of an hour, which is pretty fair. So if you knew you'd be 2 minutes late, you could take things easy, knowing you have to work 15min extra either way.That seems illegal, because I guarantee you they're not paying overtime.
And if they are, I guess this rule would last exactly until someone saunters in an hour late, and they have to pay for 10 hours of OT.