A How-to on Setting up Folded Cards:

Sizes

Folded Cards are setup at double the width of the size when folded. The height of the card is the same but the length of the card is twice. 
Standard Sizes are:
10in x 7in => Folds to 5in x 7in | 8.5in x 5.5in => Folds to 4.25in x 5.5in | 8in x 6in => Folds to 4in x 6in | 11in x 8.5in => Folds to 5.5in x 8.5in