18-08-10 My clothes don't fit!

[child-of-fae]

^ plus guys get broader chests when they hit puberty

[Kamino Neko]

To end a potential point of confusion - she's talking about the band, the part that doesn't go over the breasts themselves. How endowed she is has no bearing on her band size, so changing to a guy only effects it because she grew in the process.