First of all, the word "delay" here is not entirely appropriate. You are not a rally participant and you do not have to "cross the finish line".
You can return the car the same way you picked it up, meaning anywhere and anytime. But if you wanted to get to mentioned return point and you are late, in this case you have “gap hour” which is used to to prepare the car for the next tenant. If you are able to return it within that hour, you will not need to pay extra.
In any case you need to warn us about delay at least 6 hours before the expiration of the rental period. If you delay for a longer period of time, you will be charged the usual fee: from 1 to 3 hours - half the cost of renting your car per day, if more than 3 hours, you have to pay full fee for one more day of rent completely.