This is a limitation with authorize.net SIM transaction method.
they don't offer a way too pass item specific details, only a general description for the order.
rather than rely on the Authorize.net recipe to include the item details, you should have set the checkout wizard to send a custom email. that email receipt would be able to contain the cart display with full item information.
one thing you can do is edit the cart object, and on the calculations column edit the Full details calculation to include the option columns. for example change:
[Quantity] . ' ' . [Name] . ' (' . [ID] . ')'
[Quantity] . ' ' . [Name] . ' (' . [ID] . ')' . ' ' . [color] . ' ' . [size] etc...
make sure to use the correct case for each of the column names. the full details is used for the order description.
NOTE: Authorize.net has a limit of 255 characters for the description filed, and it can contain only alpha numeric characters, no special characters.