The Field Settings on Amount based fields can differ slightly if the amount based field is the Gift Amount field on a Gift record or an amount field in another area of Raiser's Edge.  As of version 4.6, it is not possible to update an Existing Gift and the Gift Amount field must be populated for a New Gift to be created, so there is no option to select for the Only Update Values for section.  Users can, however, used the Conditionally Update Values as a way to suppress Gifts from being created. The Data Transformations here also allow users to adjust the amounts dynamically if need be.