Broken Souls - S6-E2
Character mistake: At the very end of the episode, a chess board is set up wrong, the initial position must have the white queen on the white square (d1) and the black queen on the black (in this case red) square (d8). They set up all the other pieces correctly except the kings and queens should be reversed.
Answer: They are using the accepted names of the bombs. During World War 2 the Germans used the metric system and produced bombs ranging from 50kg to 2500kg. Referring to the weight of the bombs in pounds (or fractions of tons) risked confusing the situation and would require someone to understand how to convert from imperial measures to metric, not an easy thing to do when under stress.