Greetings everyone. I'm new to the site and joined so I can gain insight on some perplexing fashion inquiries. Especially as it pertains to sizing. I own an online boutique, but have been running into constant questions regarding sizes and conversion of sizes and was wondering if someone can please assist me. I know that there are different sizes for shoes and clothing based on the country you reside. However, I don't understand the what countries to associate the initial sizes with. For example, one of my size charts states the following:

Small - Bust 15 Waist 12 Hip 21

I thought it was initially Asia size charting, but after looking it up, their sizes don't read with such small numbers. Does anyone have any ideas as to what these numbers represent please?

Thank you in advance for your responses to my aforementioned inquiries and hope I explained properly.

Cheers,
SSCB