The context of the following conversation is Sydney worries about blowing a tyre on the highway, she buys two spare tyres even though the car already has one.:
Sydney says Maybe it's irrational, but having a blowout is one of my biggest fears..
The friend responds Statistically it's very unlikely to happen. Don't be nervous about it..
Sydney responds I'm trying not to be. But I bought a couple of spare tyres, just in case..
The friend responds A couple of spare tyres? Doesn't the car already have one?.
Sydney responds It does. But I wanted two more, just to be safe..
The friend responds Sure, if it makes you feel better. But the chances of having a three tyres blowout are basically zero..