The spoke lengths you are giving are for a 605 ERD not a 603 so I assume you chose Mavic Reflex (ERD is Mavic's Nipple Seat Dia + 3mm for nipples) with a 605 ERD and mis-read it as 603. If that is the case, you have figured out how to use the spoke length calculator. Now you need to double check the ERD. The preferred method is shown below and better described by Mr Rabbit. The 605 ERD shown in the calculator was derived by measuring the distance from opposing nipple seats and then adding 3mm for the head of the nipples. The latter method will work most the time, but if you want to be sure, best to use the former as rim ERD's can very even amongst the same model over time.