Who Can Math Before Coffee?

(I’m a flight attendant. I ask a passenger what she wants to drink.) 

Passenger: “Coffee… black with two sugars, please.”

(I repeat it back to confirm and she nods. I hand her a coffee with two sugar packets on the side.)

Passenger: *as she takes it from me* “Two more sugars, please.”

Me: “Oh, sorry, I thought you said two.” 

Passenger: “I did. But when I said two I really mean four.”

Me: “…”