What’s the difference between if I reserve a public IP and not?

When you reserve a public IP, we take care that the IP cannot be used by other users, so you can use it freely.

How am I charged for reserving a public IP address?

The price stated at the Reserve IP Address page is the price for 1 month (until the end of the current month). On the 1st of the following month a fee will be charged again. Your credit of 1 month fee will be immediately held. You will be charged in full until the end of the month even if you only create it for a few minutes or hours and delete it.