Boob trouble

So my boobs are two different sizes(like normal) but they are like really different in sozes. On is like a 34-36 B and the other is like a 32 A. But it’s my left one that’s super small, and I didn’t think it was something all too concerning till me friend told me that it should be bigger because it’s above my heart? Is this true? And does anyone know how I can even them out a little bit?