Welcome to FT!

To give the short answer to your question, yes, Dollar was following the industry standard.

To give you the long answer, the industry standard is typically a 30-minute grace period beyond the 24-hour mark of each rental period (ie. if you pick up a car at 11am, you have until 11:29:59am the next day to return it without incurring extra hour/day charges). After the grace period you will be charged for each extra hour until the extra hours exceed the price of an extra day (and since extra hours are typically priced at 50%-75% of the daily rate, it only takes ~1.5-2 hours to reach that point).

Assuming you rented your car at 9:41pm the previous day you were almost 2 hours late per the 24-hour rental clock when you got to the counter at 11:30pm so it makes sense that an entire additional day of all services was charged.

Hope this helps!