In the vast majority of case when you are carrying items in your inventory each item you carry takes up its own slot in your inventory. However when you are storing items in your bank the same items, for example iron bars, would only take up a single slot but have a numerical number on the item to represent how many of that item you have. Now if you’d like to trade high quantities of items faster than 28 at a time then you are able to withdraw items in noted form which basically withdraws the item as a note and the note is tradable and then the owner of the noted items can redeem the items by depositing the note into their own Runescape bank account.