Insurance policy

I discovered 2 errors on our insurance policy for one of our cars.
It stated that we didn't have an alarm and immobiliser fitted, but we do have both. It also said that the car is parked behind a locked gate at night, which it is not. One of these is "positive" and one is "negative" for the premium we pay, or so I thought.
It turns out that it is only the "negative" error, that the car is not behind a gate, that affects the premium and makes it more expensive! :-(
First I was surprised, but after thinking about it for abut 1.2 seconds I realised that it always works this way with all insurance companies and banks!