second set is the winding of the motor. the lower the number, the higher the kv, hence the "hotter" it is. It means it produces more RPM at a given voltage. Good for speed, or gearing purposes, but if you're tryitn to turn larger propeller, it can't (draws too much amps).

in general, higher KV motor is more efficient, but not able to swing big propellers (unless geared)

HTH
Josh