Create Sales Contract from Business Opp Sales Values not copying

I’m trying to create a sales contract from a Business Opportunity.  In the Create Sales Contract dialog, in the lower section I set my line no, description and set my Calculation type for Sales Value and my calculation method of Rate Only and Fixed.  When the Sales Contract is created, the only values that come over from the Opportunity and ones where I’ve set the calculation method to Fixed.  Does anyone know why the values when I am using Rate Only are not coming over to the Sales Contract?