As someone with smaller kids, the light is off with no occupancy, comes on at ~20lbs seat weight to indicate the passenger air bag is DISABLED, then goes back off at some heavier weight (~60ish?) to indicate it is armed/functioning normally.
OP, just as an FYI, if you like RDS data on your radio, you have to press the button once, then use the adjacent select key to turn on or off.  If you press the RDS button multiple times it will cycle through other options that you can enable or disable with the select key.  Just info you might otherwise never think about (or assume it doesn't work, for years, like I did).