There is a better condition you can use for the first part of the trigger, in the list you will find the option 'Presence of an item in the cart', then just specify the id number for the item and and 'exists'. Next you will need to use the 'Quantity of a specific item in the cart', then you just specify the id of the item and it's greater than equal to value for the quantity.
This should be followed by the flat rate calculation and just enter the dollar amount for the shipping charge.