quantity of item uses the item ID
Calculation, based on quantity of item: Quantity of item 1 timex .10
would apply only if the item with Item ID 1 where in the cart
What is the ID of the item that is in the cart?
To help in troubleshooting issues like this, i like to create a separate cart display page, and on the second screen of the cart display manager, set it to show all columns, that way you can see all the info in the cart, including IDs.