Problem with relay shield or some mistake with code?

mmm this is very strange.....i think that i miss something..... the relay state must be on when the temperature is under 30°C. in this case to activate the relay n°1 (plugged with pin 5) i think that i must to put in HIGH state the pin but doesn't work! if i put the pin state LOW the relay work perfectly!!! i cant understand that...someone could explain me why??