Great question. If you want two sets of spoons, select the $60+ Reward Level (THE SET), but adjust your Pledge Amount to $120. When the campaign ends, we'll send out a backer survey to make sure this is what you pledged the extra funds for.
This applies to any "add-on" items. For example, if you want 2 of the Standard Classic ($25), select the $25+ reward level (STANDARD CLASSIC), but pledge $50 toward the project.
If you want the Set of spoons ($60) and a second Standard Spoon ($35), select the $60+ Reward Level (THE SET), and pledge $95 toward the project.