I calculate the cleanup time before I start backing up the database. The reason for that is to protect against a scenario where you delete a backup that you have just performed. Please send me a mail (http://ola.hallengren.com/contact.html) if you are interested in more details on this.
Another thing is that you may have variations in the time when the backup finishes.
Because of these things you need to set the CleanupTime to 23 or 22 hours in your case.
Ola Hallengren