Completely misleading, alas.

The vertical scale is megatons, and is 1-dimensional, but the graphics are 2-dimensional, and thus make the 50 Mt bomb look much bigger than it should be, not to mention the actual bombs' effects were spread over 3 dimensions, which is why in real life, the height of the Hiroshima bomb's cloud was ~15% that of the Tsar bomb, instead of the 0.03% this terrible chart shows.