[RichardJ]

I agree with 68 POS. 2400 is way, way too high. Not only is there no reason for it, cold thick oil puts an unnecessary strain on the distributor drive to the oil pump.
Somewhere around 1200, IMO is usually all that is necessary.
With the choke closed, the rich mixture would cause the plugs to foul at normal idle speed of 600. By increasing rpm to a higher idle when cold, the extra air lets the engine run smoother until the engine warms.

Choke opening and high idle rpm should be tailored more to your climate conditions than any book setting and only after timing, mixture and idle adjustment are done.