Gday Cosmo. I dont know the reason for the light, but I have a thought on the matter.
The light means the wheels are retracted and locked up; the doors are closed and the wheels are in their bays. This might prevent you from exceeding any landing gear limiting speeds and damaging either the gear or the undercarriage doors. A floating gear might cause such damage, so this light may be a way of confirming the undercarriage status.
Kermie
