It doesn't matter much. In the Qin Dynasty, the Yueguo region refers to Zhejiang, Fujian, Guangdong, Guangxi, Guizhou and northern Vietnam, but it was only in that part of Zhejiang that the country was born. At the end of the Qin Dynasty, Zhao Tuo established South Vietnam in today's Guangdong. You can know from its name that it is the southernmost part of the Vietnam region. Vietnam didn't officially have a country until the Song Dynasty. Of course, Vietnamese officials do not admit that their history is so short. Vietnam had several names at first, and China officially recognized two official names of Vietnam: Annan and Vietnam. The name Vietnam was only taken during Jiaqing period, when Vietnam applied to change its name to South Vietnam. However, after discussion, Vietnam is in the south of South Vietnam and has nothing to do with it, but the northernmost part of Vietnam overlaps with the southernmost part of South Vietnam. Therefore, the approved country name of Vietnam, so-called, means southern Vietnam.