In the tutorial for the Size options, the select list is created to pass the option ID to the lookup recordset.
In the Add to cart bindings, the Size Name and the Price Increment column in the add to cart button are bound to the corresponding columns in the lookup recordset.
The option ID does not get stored in the cart. It is used to filter a recordset and lookup the option name, and option price increment.
it is these values from the lookup recordset that are stored in the cart.