paperwork i have says outside temp 
EDIT
sorry it reads Ambient temp so yes probably cabin
reheating authorisation zone.
The injection ECU works out the heating requirement in the passenger compartment when starting as a function of the curve.
Example 1 :
l Engine coolant temperature=40 °C.
l The ambient temperature=- 10 °C.
l The temperature conditions are in the additional heating operating zone.
EDIT
sorry it reads Ambient temp so yes probably cabin
reheating authorisation zone.
The injection ECU works out the heating requirement in the passenger compartment when starting as a function of the curve.
Example 1 :
l Engine coolant temperature=40 °C.
l The ambient temperature=- 10 °C.
l The temperature conditions are in the additional heating operating zone.