Twin A?

Puteri

Hi guys. I'm from Malaysia. I had a scan yesterday & was rly hoping for the doc to tell the gender of my baby but she said she couldnt tell bcs it's not sure yet at "this stage". Anyway, I was wondering if any of you know what TWIN A means in this picture? I only see one baby & when the doc scanned me, she didnt tell me if i was going to have twins. Please help!