Getting fitted for a bra

well today I got fitted for a bra and I was told to remove my shirt and so i did. They used the tape and did some things, but I didn't understand what they were. Anyways my results were 58C and my mom was there and said that couldn't be right because I have Itty Bitty Titties. Then my mom made me take off my bra and get measured again. Then it came out to be 42B. I was mortified to be topless. Was that right of my mom?