The number doesn't seem to shock him, horrify him or impress him. He accepts it as a fact, because he has no reason to disbelieve what she's saying.

"Explosives are a very useful tool to have at hand," He agrees, because he's used them himself. They are messy though, and not ideal for a setting where there's innocent people who might be wandering around. Or children.

"So are traps, if you can rig them. That's not always a luxury I had time for." He pauses, and then because he realises he's not actually even sure, at this point, he's just got a vague idea, he interrupts her in giving the rest of her answers.

"What actually... is a walker? I know it's a body, with a virus. Walking around. But... how?"