If A goes left and D goes right, that’s two actions: move left and move right, so your two buttons are done. Nothing more allowed.
If, however, the A and D buttons both move forward at the same speed (there’s nothing different about what they do) then that’s one action, and you can use another “button.”
You can check out the FAQ on our past two button jam for some more details, and also games for inspiration including Vimlark’s winning game.
Hope that helps, and good luck on the jam!