The banner that I use calculates the money saved by using the price per pack info that you set but it considers the price per pack to be a pack of 20. If you
buy packs that are different size (25, 30) you have to adjust the price so that it is for 20 to get an accurate savings figure.
ex. divide the price of a pack of 25 by 25 and multiply by 20.
Relax, Enjoy!