It depends on their contracts. If the contracts make them exempt workers (meaning they don't get overtime even if they work >40h, which almost certainly was the

It depends on their contracts. If the contracts make them exempt workers (meaning they don't get overtime even if they work >40h, which almost certainly was the case) and also require them to work at least 40 hours a week or have the difference counted as vacation time, then the time cards could be used to ensure that the employees are meeting the 40 hour minimum, but the company wouldn't owe the people anything even though they were now measuring that some of them were working, say, 50 hours a week.