What does a hold for preauthorization mean and why is it different than the actual amount?

Whenever you use your Debit card, a preauthorization is electronically transmitted to us by the merchant to hold those funds in your account until the transaction can be processed. Sometimes, the merchant will put through an amount different than the actual amount. When the charge comes through, the preauthorized hold is released as long as the amount on hold and the actual amount charged are identical. If they are not the same, the hold is not released until the expiration date, which is 3 business days after the preauthorization has been put through.