It's your CDP. If you don't have this special benefit from a CDP, you can return up to 29 minutes late, after that they charge 1 hour, after 1hr29 they charge an extra day.
If you reserve with Amex Platinum CDP you get 4 hours grace period, for example.
How to know for sure? Probably best to call Hertz unless your company has some internal documentation for rental cars, on a page or site somewhere where the CDP is listed. -- Good luck!