Sub-asians are basically Indians. India is a part of Asia, so a region in Asia. But because it is a subcontinent, it is resulting in the perplexity of others not knowing if people from India are considered Asian or not. This is where the word Sub-asian comes in, because Indians are from a subcontinent(duh) they are called Sub-asian -not entirely considered Asian but also not considered Caucasian.
In a discussion:
Person 1: I'm pretty sure people from India are Asian. After all, India is a region of Asia
Person 2: No, India is a subcontinent, there's no way they're Asian
Person 3: Well, you're both right. India IS a part of Asia but they are ALSO a subcontinent. Thus, the result of them being Sub-asian