Cynthia was left with 67 -13 = <<67-13=54>>54 potatoes after making wedges.
She used 54/2 = <<54/2=27>>27 potatoes to make potato chips.
Cynthia made 13 x 8 = <<13*8=104>>104 wedges.
She made 27 x 20 = <<27*20=540>>540 potato chips.
Cynthia made 540 - 104 = <<540-104=436>>436 more potato chips than wedges.
#### 436