Hahaha, [he can't help but laugh, not surprised that she'd think he was slacking off. On the contrary, really.]

I don't slack off too much. I take extended lunches every now and again, but I assure you all my work is meticulously finished every day. Even if I show up late. I'll stay late if I have to.

[Really, that's just how he is- he knows exactly how much time he needs and finishes his projects, no matter what they are, with a surgical expertise.]

So don't worry too much about me. Who's going to fire me, anyway?