What ၀ means
It is the zero digit in Myanmar-script numerals. In ၂၀, it leaves the ones place empty so the number means 20; in ၂၀၀, two zeros leave the ones and tens places empty, so the number means 200.
The Myanmar script developed from a script of southern India related to Brahmi, an ancient Indian writing system, and was adapted to write the Mon language around the eighth century. Myanmar-script inscriptions reach back to the eleventh century; the oldest surviving Burmese inscription is dated AD 1113. Early inscriptions were dedicatory or religious.
Don't confuse it with
1Questions people ask
1Why does ၀ show as a box on some devices?
Because that device's fonts have no glyph for it. The character is still correct and still copies correctly — the box is a missing glyph, not a broken character.
How to type ၀
၀\1040Codes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.

