Can somebody explain AC/Heat push button control chart for 68-70 Chargers

[Blakcharger440]

The AC/Heat push button control chart is set  up like this.

----------------------------OFF-----MAX A/C-------A/C-------HEAT------DEFROST

Fresh Air Door-----------Closed......Closed..........Open.......Open..........Open
Recirculating Door-------Open........Open..........Closed......Closed.........Closed
Air Cond Door------------Open........Open..........Open........Closed.........Closed


Could somebody explain this because for some reason it doesnt make sense to me right now.