Electric furnace wiring
You furnace looks like it is an approximately 20-KW model.  It requires no neutral.  It is not asking for a neutral.  It requires A phase and B phase from a single phase residential service.  And the wiring layout will be as follows: from the top, first breaker, A phase on top and B phase on bottom, and Second breaker A-phase on top and B-phase on bottom. You will need two runs of 6-2 copper or two runs of two 4awg aluminum with ground.  In the house panel you will need two each new 60-Amp breakers.