I'm not sure what the article claims here. This is the first dated inscription but the positional arabic notation (with a zero like glyph) had been in use for at least 300 years earlier. If you consider other place value systems the concept of a 'separator' goes back much farther.

This isn't necessarily evidence that they understood zero as a number as opposed to a concept. By 1000 in Europe they used a symbol as a placeholder that looked superficially similar to our modern glyph of zero. When explaining it, however, it was clear it was simply a placeholder that could always be omitted and was "sometimes useful" and was absolutely not really a number. It isn't clear that the glyph used here or in Europe was anything more than an elaborate 'dot.' It certainly didn't seem to be be transmitted as a recognizable glpyh but each culture rendered it in the way most convenient as a counting and placeholder aid.