My levers are set about 15 degrees below horizontal, the limit being how far back and low you need to get when going down extremely steep slopes and still reach the lever.
Note the hydraulic reservoir on my clutch, plus the little adjusting screw on the short side of the lever, that’s the true sign of a one finger clutch 
This picture shows how little you need to apply it to completely disengage the clutch:
…and there is still lots of adjustment for riders with shorter fingers. These are fully adjustable reach controls
