Despite the pre-translation implications that this picture poses, it is in fact a "breast" comparison chart ...
Though it's absolutely hilarious if you interpret it as a penis size chart, because it suggests the guy under "None" is dickless.
Also, that Armin is so far behind "None" that he's dumped into a woman's "breast comparison" chart, since that's the label right above him.
...Seriously, though, is there any way for Armin to graduate boot camp without the slightest bit of visible muscle? Even little Christa has to look more buff than Armin is drawn, here.