The cooking time will depend on the size of the lamb joint and the type of Air Fryer you use so a digital thermometer is the best way to ensure the lamb is cooked to your liking.
ROAST LAMB INTERNAL TEMPERATURE GUIDELINES
The best way to check your lamb is cooked to your liking – and safely – is to check the temperature with a digital thermometer. Insert the probe in the thickest part of the joint, avoiding the bone. The guidelines below are for the UK, it is possible that these recommendations are slightly different in other countries.
Find it online: https://allguiderecipes.info/air-fryer-roast-lamb/