Make sure to choose the 2-pack option for each bundle step. For example for bundle step 1, I chose 2 pack cherry shelves. Then for bundle step 2, I chose 2-pack brown shelves. Total of 4 shelves for $32 .
For some reason, it charged me $13 for each 2 packs, making it $26 , but I am not sure if this will work for everybody. Attaching the $13 screenshot below.