When I started a low dosage of hormones, I did not expect any breast development at all because I was in my sixties and my mother was not particularly large in that area.
Now I fill a 38C and use forms to weigh them down a bit so I don't look too "perky" (my wife's term) for my age. In male mode, I wear a one-size-too-small undershirt and loose clothing to hide the shape.
As the saying goes, your mileage may vary...