I'm not sure what a bra top is, but if it's not a real bra, then you never know. It might work. You won't know until you try it on!
I find bra sizing to be all over the map. Went bra shopping with my teens recently, and it was quite frustrating. I wear a 34B in Chantelle, and that brand fits quite well, but my measurements suggest I should actually be in a 32C. It's true that the 34 band inevitably loosens up too much, so I wouldn't mind finding a 32 because it'd probably last me longer.
However, every single 32C just doesn't fit me right. The cups are too small. I have sized up to a D. In one style I took a DD... shocking! I nearly bought that one -- it was different style to what I usually wear, and came in a cute color. Then I tried it on in a 34 just to compare, and the C cup fit almost exactly like the DD?
So confused!
Ultimately I gave up and figure I will go back and try again when I'm fresher. (I always replenish bras in August).