Is 32dd considered big? why is the alpha size of it is small?

I've never owned a sports bra before and when i tried buying i brought a medium and a large one to the fitting room and the staff laughed at me i didn’t know whats the equivalent alpha size was so it was just a complete hunch. I thought 32dd is considered big.
Is 32dd considered big? why is the alpha size of it is small?
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