Dollar - Underage Fee

Hi,
I have a question and I cannot find the answer anywhere on the web.
If I rent a car for 1 day and 3 extra hours, will I be charged the underage fee for 1 day, 2 days or pro rated for the 1 day and 3 hours ?

Thanks,

Yes, any daily charges get carried over to a second day's charge if your rental exceeds 24 hours. But why bother when you can get NO underage fee with Hertz, PC 126884?

Well, price for one day without charge at dollars is $26, price at Hertz is $87 so even with $25 underage per day it's still a lot cheaper.
Thanks for your reply ;)