Lady Saxophone
▧▧▧ ♬ ▧▧▧
Most likely the items are spread out across multiple pages?
For example, if you have two Ruby caches on your first page, and one on your second page, the item stack on the first page will only display "2", but if you click it, it will show you how many exist in your entire inventory.
Item stacking is interrupted by page breaks, so it's most always going to give you the right number.
▧▧▧▧▧▧▧
oh okay well thank you c: